We all know the importance of 401(k)s and savings accounts, but even the tightest budgeters should squeeze in one more money-saving measure: the rainy-day fund. Reasons to draw from your RDF might range from an impromptu trip to New Orleans to a suddenly defunct boiler. “Americans spend an average of $725 per person on out-of-pocket health-care costs each year” — think copayments, prescriptions, uncovered expenses — “and we don’t budget for that,” says Neale Godfrey, the author of Money Still Doesn’t Grow on Trees (Rodale, $11 on www.amazon.com). Start by making a commitment to save in small doses, she says: “This is not about making big life changes.” For example, make a habit of taking a bus instead of a taxi; rent videos instead of going to a Friday-night movie; carry a thermos and a water bottle instead of buying coffee and water at work. “One night a week of not going out to eat could save a couple $2,000 a year,” says Godfrey. Judy Lawrence, author of The Budget Kit (Dearborne Trade, $11.50 on www.amazon.com), recommends always paying with dollar bills, so you accumulate change — and then immediately putting the coins aside. “Little bits can add up quickly,” says Lawrence, and that’s the key. Once you’ve saved, tally the amount, keep the cash separate, and deposit it as soon as possible into your RDF. “It’s too tempting to spend it if you don’t have a real plan for it,” says Lawrence. Either open a separate account or put the money into a special drawer (very high or low, to help fight temptation). Out of sight may be out of mind, says Lawrence, “but when you want it, you’ll know where it is.”