Before each ride: Squeeze the tires. If they don't feel firm, look on the sidewall of the tire to find a set of numbers. The tires' pressure should fall in this range. (For riding on roads, choose the higher number; for riding on dirt, go with the lower number.) Most bike pumps have a gauge that pressurizes once attached to the tire's valve. No gauge? Inflate the tires until there is no give. But "avoid high-pressure compressed air lines, like you find at gas stations, because they're regulated for cars, not bikes," says James Stanfill, the manager at the R&D Bicycle Shop, in Morgan Hill, California. For more tips, see How to Fix a Flat Bike Tire.
Every month or so: Test the brakes. While standing, press the brake levers to see that the front and rear pads firmly grip the sides of the tires. Also pay attention as you're riding: If you hear weird noises or notice that stopping requires extra pressure, hit the repair shop, says Michael Degutis, the service manager at River City Bicycles, in Portland, Oregon.
When the chain is dry to the touch: Clean and oil it. First lay down newspaper to catch splatters. With a rag, wipe debris from the links. To remove caked-on mud, spray a degreaser, like Simple Green All-Purpose Cleaner ($5 at supermarkets), on the chain and gears, scrub with a soft brush, then wipe with a rag. Mark one of the links with tape so you'll know where you started. Apply a drop of bike lubricant, like Finish Line Dry Lube With Teflon ($6 for two ounces, amazon.com) on each link as you slowly pedal backward by hand to distribute the oil. Blot away the excess.
When the bike is dirty: Do a surface cleaning with a rag moistened with glass cleaner. Take care to avoid the chain and the bearings at the center of each wheel.