Can you double your investing dollar?

How's this sound as an investing goal: Double your money in two years.

Ambitious, probably, but that's the goal set by All-Star Team trader Ken Kam, our defending Strategy Lab champ. And after 18 months running a mock portfolio in our game, he's on that pace, with a 63% gain. And every step of the way, he's shown readers how to do it.

Over the next six months, we'll see if he can finish the task -- and stay ahead of five other top investing pros while he's at it -- in the 16^th round of our stock-picking game.

Returning to the game with Kam are two other veterans: ever-steady Kelley Wright (our High IQ trader), whose focus on relatively safe, dividend-paying stocks hasn't kept him from beating the market soundly over the past year in our game; and Robert Walberg, our Dog Pound columnist, who focused on market dogs last round and found several that went on strong runs.

New this round are Tobin Smith, founder of ChangeWave Research, who's own ambitious target is doubling the market's return; Nicholas Vardy, who's emerged as a top global-stock guru at a time when world markets are roaring; and Price Headley of BigTrends.com, who correctly called the big tech correction and has earned a reputation as one of the best market timers around.

They'll test six very different strategies in a volatile market, which means there's money to be made if you stay on your toes. You'll learn what works for them, and perhaps find something that works for you.

Now: You can play

We'll have more on everyone in a minute, but first, we're trying to line up a few more players. You're one of them.

For this round, Ken Kam and his team at Marketocracy have helped us put together the Strategy Lab Open, a way for readers to play along with the pros as the round rolls on.

You can sign up now, pick stocks, run a portfolio and blog about your picks, and we'll follow the best in this space every Friday. At the end, we'll talk to the best performers and pick a winner who we'll invite to be the next Strategy Lab amateur in the first round of 2008.

You can read all about the Strat Lab Open here and sign up to get started at StrategyLabOpen.com.

Lessons from top investors

So what's Strategy Lab, anyway? In short, six months, six traders and a simple challenge for each of them: Take a $100,000 portfolio, make it grow and teach our readers how to do the same.

For more than eight years now, we've selected top investing pros with different strategies for a friendly sort of competition. It's more an educational effort than a contest, so think of it as a demonstration sport.

We set up the investing pros with mock portfolios and some simple directions: Outline your strategy for our readers. Trade for six months, explaining each move to teach people how you work. Use your methods to make as much mock money as possible.

In the end, we award bragging rights and ask the top players to return, along with three new faces.

Six months isn't a long time in the market, but it often makes for a wild ride. Take Round 15, the first half of 2007, which saw a huge market drop early on, then new highs for the Dow industrials ($INDU) and S&P 500 Index ($INX). Our traders struggled to stay even for much of the round, then bounced back strongly. All three returning players ending up beating the market. Here's a little more about them:

Kam, who also came out on top in Round 13, runs a mutual fund as well as the Marketocracy.com Web site. Like those ventures, his Strategy Lab portfolio is fueled by the contributions of the tens of thousands of everyday investors who run model portfolios on Marketocracy. The best of the best become part of his m100, his All-Star team. They can even earn cash for their research, so maybe they're semipros, but we like to think of them as amateur investors teaming up in the market.

Kam finished Round 15 with a 16.6% gain, not his best performance but more than double the market's, keeping him on pace for his overall goal: a portfolio double in two years. In fact, if we let him compound gains from round to round, he'd be up some 77% in 18 months.

Wright maintained a steady pace ahead of the market through most of Round 15, finishing with a 10% gain, roughly 4 percentage points ahead of the market. And Wright, managing editor of Investment Quality Trends, did it mostly with big, safe, dividend names such as McDonald's (MCD, news, msgs) and General Electric (GE, news, msgs). His focus is on blue chips -- and more specifically, stocks his system defines as "select blue chips" based on fundamentals, dividends and other substantive measures. But he's not afraid to take a few chances. He held snowmobile maker Polaris (PII, news, msgs) well into the summer, and still turned in a tidy profit.

Here's an apt comparison. Kam says his picks would work well as the riskier portion of what's called a core-and-edge portfolio, with a core of big, solid stocks and a portion set aside for taking chances. If so, Wright's picks could make up a fairly profitable core.

Walberg's picks would fit in the edge as well. He has specialized here in picking battered stocks the market hates -- and specifically, picking them just before the market changes its mind. That can be a tough game in a volatile market like the one of Round 15, but downturns do seem to bring some of these stocks up.

While he finished just a couple of points ahead of the market, he found big gainers like Navteq (NVT, news, msgs), up 25%; Cogent (COGT, news, msgs), up 20%; and Chico's FAS (CHS, news, msgs), up 11%. Could an all-dog portfolio come out on top of our game? If the market is as volatile going forward as it has been through June and thus far in July, maybe.

And now, more on our three new players:

ChangeWave Investor Tobin Smith specializes in change. He's constantly looking for the next big waves, targeting trends and companies doing transformational work in their fields, and aims to catch those waves early on for big gains. Doubling the market every year, he writes, can be the key to "an earlier retirement, or a better retired life (sitting around smoking cigars and drinking mint juleps)?" He'll be someone you recognize if you've been to a Money Show, watch business on Fox News or really follow the world of investment advisers at all. He co-stars on "Bulls & Bears," cable television's No. 1-rated investment program.

Global Guru Nicholas Vardy works from London and publishes The Global Bull Market and several other newsletters. He specializes in tapping booming foreign markets using stocks and ETFs readily available to U.S. investors. He, too, frequents The Money Show and appears all over cable news. A graduate of Stanford University and Harvard Law School as well as a former Fulbright scholar, he's also the founder of the London Junto, a monthly gathering where leading London hedge-fund managers and investment professionals meet to debate the top investment issues of the day. The man is tied in.

The Accelerator, Price Headley, is a technical trader who takes an unusual approach to market timing. In his strategy statement, he writes that since "most investors time the market very badly, so those who do the opposite of the crowd at the major extremes tend to have a major advantage." The founder of BigTrends.com and author of "Big Trends in Trading: Strategies to Master Market Moves," he returns to the game after being tripped up by short positions in his last round way back in 2003. Shorting is a tough game to play in Strategy Lab, so we'll see where he goes this time.

And now, the rules

Here's how it works:

We give each trader a hypothetical $100,000 portfolio to manage. The traders are free to deploy the cash using their unique strategies as they see fit. Some might choose to invest all of their money on the first day. Some might never be fully invested.

We do ask them to stick with major-index stocks, and avoid extreme small caps -- companies with less than $100 million in market cap and fewer than $500,000 worth of shares trading hands each day. Starting this round, we also won't allow players to put more than 25% of their portfolios into a single stock.

But there is one requirement that makes Strategy Lab a great place to learn. Before the strategists can make a move in their portfolios, they have to tell you about it in their journal entries. So, before a single stock is bought or sold, you're going to know about it so you can watch the trade develop and learn from the process.

To keep track of the Lab's activities, you can check this page for new journal entries and a weekly summary of the latest Lab action. When a new journal is written, we'll post a link next to the strategist's photo. Don't worry. If you're trying to follow a trader's every move, you won't have to check this page a thousand times every day -- the strategists are allowed only one journal entry per day.

If you want to see what positions a strategist is holding, look for the "Portfolio" link at the top of every journal entry. You will find a link to the pro's biography as well as a strategy statement that explains his investment philosophy. You can also find a list of every journal entry on the strategist's "Transactions" page.

Round 16 will run roughly six months. At the end, we will tally the portfolio totals and invite some of the top performers back for the next round.

If you want to discuss the latest Lab activities, have a question for the strategists or just want to talk about investing, check out the Strategy Lab message board. In a hurry and don't have time to drop by the Lab this week? Sign up for the Strategy Lab Newsletter to receive this weekly report by e-mail.

And by the way, Strategy Lab isn't a contest per se. It's a teaching experience, as different pros put unique strategies to work. But you'll find there's more than a little intramural rivalry, and that makes it all just a little more fun.

What happened in Round 15?

Round 15	1/8/2007-6/28/2007
$116,660	All-Star Team	In his third round, Ken Kam once again capitalized on the wisdom of users of his Marketocracy.com Web site to soundly thrash the market, staying on pace for a two-year portfolio double. He didn't get an actual stock double this round, as he had in each of his past two rounds, and in fact his worst stock was one that had nearly tripled in Round 14: U.S. Global Investors (GROW, news, msgs) was down about 30% this year, and a 15% loser for Kam. But he scored a 63% gain on drug maker Elan (ELN, news, msgs), a stock he's been following for some time now. His position on Valero Energy (VLO, news, msgs) was a 40% winner,and he gained 20%-plus on Occidental Petroleum (OXY, news, msgs).
$109,546	High IQ	In his second round, Kelley Wright once again topped the market by a nice margin with a safe-and-sane portfolio that seldom took a hit even in what was a very volatile market. His focus is on what a proprietary system defines as "select blue chips," with a little more leeway than the standard definition and a strong focus on dividends. It gives him room for giants like Coca-Cola (KO, news, msgs) and General Electric (GE, news, msgs), both solid winners for him this round, and smaller names like Polaris Industries (PII, news, msgs) and Eaton Vance (EV, news, msgs) -- his best with gains of 24% and 27%, respectively. And really, the thing about Wright is that he's seldom wrong. He's down on just three of the 13 positions he held at the end of this round. His biggest decline was just 4% on Cardinal Health (CAH, news, msgs). Last round, he had just one loss that was more than chump change.
$107,997	Dog Pound	Robert Walberg faced an interesting challenge with a fairly limiting strategy: His portfolio of market dogs required him to find not only unloved stocks the market was wrong about but flagging those harried hounds that investors would decide to adopt during our six-month round. He found more than a few. Navteq (NVT, news, msgs) grew by 25%; Cogent (COGT, news, msgs) jumped more than 20%; Chico's FAS (CHS, news, msgs)was good for 11%. He took some lumps along the way, too; Las Vegas Sands (LVS, news, msgs), one of his late moves, slipped 7%. But the losses were fairly limited; perhaps it's easier to identify the bottom than predict when a stock will start back up.
$104,824	WStreet Strategist	Ever optimistic and a fine writer, Charles Payne missed beating the market (and finishing higher in our little game) by exactly one trade. Payne jumped out to an early lead in the game with, ultimately, a 27% advance on salesforce.com (CRM, news, msgs) in our first few weeks. He also finished with a 25% gain on Joy Global (JOYG, news, msgs). But he was admittedly "early" on home builders and dropped 27% on The Ryland Group (RYL, news, msgs). By really, the tough trade involved using what was, for him, a rare sell limit on JDS Uniphase (JDSU, news, msgs) that kept him from dropping the stock and saving a good chunk of a 20%-plus loss. In six months, a little mistake can really trip you up.
$102,156	Value Shopper	Nancy Zambell's strategy requires patience as she waits for the market to catch up with undervalued stocks. That's tough enough in our six-month rounds, but she made it worse for herself by committing the cardinal Strategy Lab sin: not making her money work for her. With the market's big drop in February, having a big chunk of her Lab portfolio in cash kept her in the lead while other players bled red. But when the market got good, she had to play catch-up. And that's not her game. She ended up with double-digit gains on three of her earliest positions -- Globecomm Systems (GCOM, news, msgs) jumped 43%, while Option Care (OPTN, news, msgs) and Carlisle (CSL, news, msgs) both rose about 14% -- and mixed results on her later choices.
$91,270	CNBC Champ	Round 14 champ Thomas Ko again made things interesting with daring big bets on a number of stocks. But the go-big-or-go-home strategy that put him on top in the last round of our game (and helped him capture the win and a Maserati in an earlier CNBC competition) didn't deliver the big win this time. His best move was a 27% gain on Energy Conversion Devices (ENER, news, msgs), and he saw near-20% advances on Agile Software (AGIL, news, msgs) and On2 Technologies (ONT, news, msgs). But his most interesting move, and ultimately biggest loss, came when he went after two subprime lenders in hopes of a bounce. When they didn't he wanted to go all-in on shares of the delisted New Century Financial (NEWCQ, news, msgs), a move that Lab rules didn't allow. We'll never know what would have happened had they. But played right in real life, and played briefly, it might have been a very profitable move.
$106,840	S&P 500 ($INX) benchmark