Low Rate Credit Cards
Credit card companies will suck you in to a great offer of a low rate. This is basically a marketing ploy to get you to join them.
Obviously if you behave yourself and pay off the debt in full each month - which is the best policy of all credit cards then it doesn't matter what the rate is. However this rarely happens - most people forget to make a payment of there are insufficient funds in their account to pay off the full amount at the end of the month if it's paid automatically.
It's important you read a cards terms and conditions - as missing a payment can mean that they push up the APR to above 20% for instance.
Also even if you have done everything right - this will usually only be an introductory offer - where after 12 months they will again whack it up to whatever they have put in their terms and conditions.