Originally Posted by
belfpala
It depends on your bank. Mine charges no fees if I maintain my checking balance over a certain $ amount. ATMs, on the other hand, can charge up to several dollars transaction fee to make a withdrawal (generally, ATMs branded with your own bank don't charge you, while others do), which is why I almost never use cash.
Debit cards can double as credit cards. Most banks offer "overdraft credit" which means your debit card essentially becomes a credit card if your balance is too low. If you're at that point, however, you're already in trouble unless you keep your money in multiple accounts.
Interest on credit cards varies wildly. Typically it's around 10-12% for people with good credit (possibly lower with exceptional credit), but can balloon up to 25% or more if you miss a payment.