The most obvious indicator that your vehicle's brakes need attention is an incredibly high pitched squeal when you come to a stop. Brake pad manufacturers include a little piece of metal called an indicator on the pad itself. When the material wears down to the point where less than ¼ inch is left, the metal piece begins to touch the vehicle's rotor, doing a pretty good impression of fingernails on a chalkboard. Depending on how hard you drive, that usually means you should replace your brake pads within the month.
Occasionally, the indicator rusts and falls off, leaving you with no irritating noise to warn of brake wear. Additionally, many aftermarket and low-cost pads don’t come with a wear indicator at all. For the more observant, there are other signs that your pads need attention. If it takes you longer to stop than it used to, or if your brake pedal travels farther than it did a few months ago, it might be a good idea to get your stoppers checked. Regular pad checks are a good idea and require little more than removing a wheel and knowing what to look for.
Rotors are a little trickier, as they can usually last through two or three sets of brake pads before needing to be replaced. If your steering wheel wiggles in your hands when you come to a stop, your rotors are probably "warped," and it's a good idea to swap them out.??