Summarize:

Most clippers come with a maintenance kit that includes a small brush. After every shave, brush excess hair off of the blades and guard. This ensures that old hair does not build up and work its way into the clipper's interior, where it can interfere with the operation of the motor. If your clippers didn't come with a brush, you can use an old toothbrush or a bristly pipe cleaner. Most clippers also contain a small bottle of lubricating mineral oil. After every several shaves, clean the blades with the brush, then apply a few drop of mineral oil along the clipper's teeth. Turn the clipper on for about twenty seconds. This allows the oil to spread along the blades, keeping them sharp and smooth. If your clippers didn't come with oil, contact the manufacturer before substituting your own oil - many household oils aren't suitable for clippers and will affect their performance. Well-maintained clippers should give you few problems. However, like any electric appliance, clippers can experience occasional performance issues. Here are a few of the most common complaints, with basic troubleshooting instructions: "My clippers make a very loud buzzing noise." Many clippers have a voltage regulator that resembles a screw on the side of the device. This can be easily adjusted with an included tool or an everyday screwdriver. Experiment with adjusting the voltage regulator in either direction until the noise stops. There is no risk of electrocution. "My clippers can't cut my hair." Your clippers may not be sharp enough or the internal motor may be losing power. Ensure that you're regularly cleaning and oiling the blades. If you clippers are noticeably slower, there may be an issue with the motor - it may be time to replace the clippers. Consult your manufacturer for warranty information. Alternatively, your hair may simply be too thick! Clear any hair that is jammed in the blades and try again with shallower cuts. "My clippers don't hold a charge." Over time, the battery in portable clippers can deteriorate. Most manufacturers can replace them - contact your manufacturer for more information. "My clipper's blades are crooked." It's possible for clipper blades to get bumped out of alignment. Realignment is not generally a difficult process, but it will differ based on the precise make and model of your clippers. Thankfully, most manufacturers will have online guides for blade realignment and amateur DIY instructions are easy to find.
Clean your clippers. Keep your clippers sharp. Be prepared for common problems.