Tip #8: If you use a credit card (and do limit yourself to one), pay it off completely every month--or don't use it, except for true emergencies.
Ideal use of credit cards takes self control and discipline. And my husband and I are two of those apparently rare people who "work the system" when it comes to using credit cards. In fact, we are the kind of people credit card companies hate! We earn point toward airfare by using our card, but we rarely (if ever) pay any interest because we pay our card off every month. In financial matters I hate being in debt more than anything, so paying that bill in full every month is always a relief.
If you don't have a credit card but have thought of getting one, I would suggest trying a debit card first (if you haven't already). Since a debit card takes money directly from your bank account, you can't use more money than you have. But it's still plastic, (way too) easy to use, and necessitates knowing how much money you have all the time--so it's good preparation for credit card use. If you find you're disciplined and financially aware with a debit card, you would probably be a wise credit card holder. Just be sure to "do your homework" and check out all the fine print before you decide on a card.
And if you're unfortunately like the average American, with $9,000+ credit card debt, here and here are some good tips to help you regain control. It's maddening enough to pay mostly principal on a mortgage; I can't imagine doing it just on daily spending!