You may already be a winner! Or so the junk-mail and email come-ons tell you. But is it too good to be true? Well, yes and no. The odds of your winning any single sweepstakes are tiny. But "sweepers," those who enter hundreds of giveaways a week, do win: vacations, jewelry, cars and cash. Whether entering pays off depends on how much time and energy you're willing to devote, and it won't be worth it unless you…

1. Do your research.

The more you enter, the better your chances, so start digging up contests by using free listings such as www.online-sweepstakes.com or the "Promotions" app on Facebook. Some sweepers spend as many hours researching sweepstakes as entering them, but sweeps newsletters, which cost about $60 a year and cull giveaways from all over, can save you time.

2. Go mobile. 

If you have a smartphone or tablet, enter extra contests while you're on the bus or waiting for your kids at the dentist. You can also try texting sweepstakes, which tend to receive fewer entries than those online, says Patti Osterheld of the newsletter SweepSheet.com. "But be sure to have a generous texting plan—it can get costly if you pay per text," she warns.

3. Enter as many sweepstakes as you can—and enter often.

Enter as often as contest rules allow (which may be daily)! To have a chance at winning, experts advise filling out entry forms for at least 30 minutes, three times a week. Repeat winners, like Osterheld, spend about three hours a week. Go to Roboform.com for a free app, which can fill out forms for you in seconds. Carol McLaughlin, publisher of This 'n' That Sweepstakes Club Newsletter, wins about one of every 200 to 300 sweepstakes she enters.

4. Work the odds.

Spend more time entering multi-prize sweeps rather than those with a single payoff, advises Gwen Beauchamp of the newsletter SweepsU.comFocus on local and regional contests, which get fewer entries than national ones. Osterheld enters around 10 per month—and wins about 50 precent of the time!

5. Play by the rules.

Pros say 20% of all entries are disqualified for being done incorrectly, so for everything you enter, read the instructions carefully!

6. Know your newsletters.

Some online favorites of pros include: This 'n' That Sweepstakes Club, SweepSheet.com and SweepsU.com.

7. Watch out for scams.

No legitimate sweepstakes will ask for information like a credit card or bank account number. Also, ignore emails with bad grammar or poor spelling, or that promote contests from other countries.

8. Track your winnings.

Even noncash prizes are taxable income. Sponsors will send 1099 forms for winnings over $600. Start a spreadsheet for the rest, and pay up on April 15.

BOTTOM LINE

If you spend 3 to 5 hours a week finding and entering sweepstakes and follow the techniques above, you'll have a shot at winning. Otherwise, it's not worth your time.