If someone is looking to trade his or her best player to you, you'll think about why it might be too good to be true. Likewise, saving 15 percent off on a day's purchase just for applying for a retail credit card has its own set of caveats.

Winning strategy: Just as you might sleep on a trade offer before you hand off a player, think twice before signing up for new credit accounts. "Don't apply for other credit in the three- to six-month period before you're going to apply for a car loan or a mortgage," says Sweet. That's because if your recent credit history includes opening or applying for new lines of credit, it can cause your score to take a hit. And the lower the score, the higher the interest rate will be on that loan you're seeking, she says.

"As a general statement, opening up multiple new accounts ... is interpreted as increasing risk, and the score might be impacted," says Barrett Burns, president and CEO of VantageScore Solutions.