Make a budget. This doesn't have to be complicated; write down how much money comes in and then ALL the money that goes out. Start with things that don't change, like your rent or mortgage, and things that are there every month like the phone bill. End with gas and groceries. Hopefully your outgoing is less than your incoming! If not, you now have a list to see where you can start cutting back.
2. Stop using credit. If you can't pay cash, don't buy it. It's hard, those credit cards are so tempting. But most credit cards are charging you a huge amount of interest. A minimum payment on most credit cards is only about 30% on the balance, the rest is interest. (Try this credit card minimum payment interest calculator. It's a little scary.) That's a serious waste of money. While you're at it, close down any credit accounts you have with no balance, it reduces temptation and helps your credit rating.
3. Don't save if you're in debt. I know it sounds odd, but it does you no good at all to save diligently at 2% if you're paying 18% interest on a credit card or even 8% on a loan. Instead send that money to your debtors to pay off those high-interest debts sooner. Even paying $10 a month above minimum payments on credit accounts will save you tons in the long run.
4. Don't buy it unless you really need it. If money's really tight, you don't really have discretionary money to spend on unnecessary stuff.
5. Shop smart for what you need. Compare prices, clip coupons, wait for sales. With small exceptions, there's really not much one can't live without for a few days or even a few months for bigger purchases.
6. Don't impulse buy. You see the perfect whatever, on sale, at a good price. You gotta get it - but don't. Walk away. Just coveting an item isn't reason enough to buy it. Give yourself some time to think about it. More often than not you'll find that the impulse will pass.
7. Start cutting luxuries. And while you're at it, redefine what's a luxury. Do you really need a cell phone? If you do, then do you really need a regular phone account? Do you really need a cable modem, or would a $15 dial-up account do? Find a second-hand bookstore instead of buying new. Cable TV, eating out, music, books and videos, all these add up to money you don't need to spend.
8. Pack a lunch. Eating lunch out every day can really add up. If you spend an average of $10 for lunch five days a week you're spending $200 a month on food. I guarantee you can brown bag it for at least 1/4 of that if you shop smart. And it doesn't necessarily mean living on bologna sandwiches.
9. Do it yourself. Learn to cook, change your own oil, mend and sew, iron. Did you know many dry-clean only clothes can be hand-washed? That changing your own oil only takes one special tool (if that) and about a half-hour? That just darning your own socks can save you money?
10. It's okay to get help. There's all kinds of help if you're in serious financial trouble. A copy of Quicken or Microsoft Money can help you get your personal expenses under control and make a debt-reduction plan. A debt consolidation service is an option. If you own property, consider refinancing for debt consolidation (mortgage interest is much lower than credit card interest). If your issue is low income rather than high debt, see what kind of assistance you qualify for. There's no shame in getting help.