In a notebook, jot down everything you buy for a few days. At month's end, scribble down what you spent for: housing/utilities, transportation, debt payment, extras (nonessentials such as concerts, movies, restaurants) and savings. Look for money spills you can avoid, says Weston, where you overspent on things you didn't need.

Once you see where your money is going, determine if your spending is in line with your financial goal. If not, set a specific cap on extras spending and decide how much you can realistically save each month. Adjust your day-to-day spending (tote bagged lunches to work instead of eating out or brew your own coffee) to limit how much you shell out for extras and increase how much you sock away. Your reward? With the money saved you can buy that overnight spa trip—or achieve your financial goal—with guilt-free cash.

All this calculating may sound like a chore but it's not. With free online calculators, drafting a budget is a cinch, taking just five minutes. Try Kiplinger's or WaMu's Budget Calculator.