The market exchanges may have posted reasonable returns in 2012, but this doesn't mean that all investors were simply running in place.

There are actually several stocks that have been killing it this year, and reading into the things that went right for them in 2012 may help you identify the traits in the stocks that will more than double in 2013.

Let's go over five of this year's biggest winners.

Arena Pharmaceuticals (NASDAQ:ARNA): up 368%
Most people will tell you that they can afford to lose a few pounds, and not just this time of year when we all tend to put on a little more weight over the holidays.

Arena's been there, and it's back with a potential cure.

When the Food and Drug Administration approved marketing of Arena's weight-loss drug lorcaserin -- the first anti-obesity medication to receive regulatory approval since 1999 -- investors flocked to the stock.

Arena's still losing money, and there are other companies with potentially promising treatments on the way. However, the appeal of Arena as it cashes in on a country full of love handles if it's not acquired outright has been too tempting to ignore this year.

3D Systems (NYSE:DDD): up 260%
There are few things as exciting as 3-D printing. The ability to print out actual objects -- from auto parts to artificial limbs -- makes this a game-changing niche that investors need to keep watching.

Yes, the easy money's been made. 3-D printing leader 3D Systems saw its stock more than triple this year, but that came after being largely ignored in last year's IPO.

3D Systems may not seem cheap at 33 times forward earnings, but the upside growth of 3-D printing is going to keep the shares at a healthy market premium for some time.

Vringo (NYSEMKT: VRNG):  up 192%
Vringo began the year as an obscure app developer. Its biggest app was a video ringtone program, hence the corporate moniker.

However, things got interesting here after it acquired some old Lycos patents related to the way that ads are targeting search histories. Vringo turned around and started suing online juggernauts that seemed to be trampling on its freshly acquired intellectual property.

Vringo didn't get the payday it was originally hoping to score. A district court judge limited the company's potential damages in its patent infringement suit. However, Vringo still closed out the year with lucrative decisions in place.

Lumber Liquidators (NYSE:LL):  up 191%
It's been a great year for homebuilders. There have been several real estate developers that have seen their shares more than double.

However, the residential realty market stabilizing has also opened the door for companies that help with home improvement projects. Lumber Liquidators is the leading stand-alone retailer of hardwood flooring.

Low prices draw in homeowners, and now the appeal is clear with home prices on the way up. Folks hoping to improve the quality of their homes through hardwood planks no longer have to worry about freefalling home prices taking their mortgages underwater.

Lumber Liquidators has blown past Wall Street's profit targets in each of this year's first three quarters. The market obviously likes to see that happen.

Conn's (NASDAQ:CONN):  up 171%
You don't often see a stock that doubled one year come back with another triple-digit return, but that's just what happened with Conn's.

The consumer electronics retailer turned heads last year with its 137% ascent, and this time it rose by even more.

Investors tend to think of Best Buy or the skeletal remains of Circuit City when they think about consumer electronics, but that isn't what Conn's is about. Conn's emphasis on appliances, furniture, mattresses, and even lawn care equipment has helped it stand out with large big-ticket items that can't be easily fulfilled by online retailers.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.