Parents spend the first several years of children's lives teaching them how to play fair. By the time we hit elementary school, most of us are pretty good at knowing what's just and what's not.

That sense of fair versus foul, though, tends to get tangled up in the world of credit cards. Some practices that seem egregious at first glance actually make sense when you understand their rationale. Other policies don't hold up so well to scrutiny, even though they're widely accepted in the industry.

What makes matters more complicated is that a few credit card issuers are bad to the bone. Some of the companies that have the most consumer-friendly practices in one area turn around and punish their customers unfairly in another.

After many years of covering this industry, fielding reader complaints, talking to the issuers and listening to consumer advocates, I've drawn up the following list of what I consider fair and foul play, plus what you can do about it.

Mystery interest rates

Fair play: charging different customers different interest rates or offering different terms, based on their credit histories.

Foul play: not telling folks upfront what interest rates or terms they'll get.

If you have a good credit history, you should get a good rate, not one that's been inflated to cover the risks of others who haven't been as responsible.

But no one should have to play Russian roulette when applying for a card. Though some issuers, including Citibank and Capital One, usually tell you in advance what rate you'll get if approved, others -- including Chase, Discover, American Express, HSBC and Bank of America -- typically only offer a range of possible rates. You might get a rate that's in the single digits or one that's over 20%.