Because US law protects you much better when you're using borrowed money instead of cash, some situations might call for a credit card and some a debit.

• Select "credit" over "debit" when using your card at checkout. Besides the whole stealing your PIN thing, it's an "authorization hold" vs. instant money snag.
• Don't make important purchases by debit.
• Don't use debit for monthly recurring charges.

Overall, debit is much harder to dispute than a credit cards. Credit cards have specific laws regulating their use. With a debit card, you're subject to the byzantine array of merchant agreements and the contract you have with your bank.

We personally like debit *because* it takes the money out quickly. Expenses can be easily monitored and their repercussions are immediate, helps thwart the slow slide into a spending spree that easy credit can encourage. (Hat tip to Larry.)