Following are all the parts on your guitar that are most likely to wear out or break and need replacing. You can perform any of these fixes yourself without doing damage to the guitar — even if you screw up.
Tuning machines on your guitar
Tuning machines consist of a system of gears and shafts, and as the clutch on your car usually does eventually (or the automatic transmission if you never got that whole stick thing), tuners can wear out. Tuning machines deal with a lot of stress and tension.
Tuning machines simply screw into the guitar's headstock with wood screws (after you push the post through the hole and fasten the hex nut on top); so if you have a worn or stripped gear, consider replacing the entire machine. If more than one tuner is giving you trouble, consider replacing the entire set. Check that the replacement machine has its screws in the same positions as the original, because you don't want to drill new holes in your headstock. If you're having trouble matching the holes of your new machines with the existing ones already drilled in your headstock, take the guitar to a repairperson.
Strap pins
Strap pins are the little "buttons" that you put through your strap holes to attach the strap to your instrument. The strap pins usually attach to the guitar with ordinary wood screws, and they can sometimes work themselves loose.
If simply tightening the wood screw with a screwdriver doesn't do the trick, try applying a little white glue on the screw threads and put it back in. If it's still loose, take the guitar to a repairperson.
Guitar bridge springs
If an electric guitar doesn't have a whammy bar, its bridge affixes directly to the guitar's body. This setup is known as a fixed bridge. If the guitar does have a whammy bar, however, it has a floating bridge. A floating bridge is held in place by the string tension (which pulls it one way) and a set of metal springs — known as bridge springs — which pull in the opposite direction, holding the bridge in balance. You can find the springs (which are about 3 inches long and 1/4 inch wide) in the back cavity of the body.
If one of the springs loses tension through age and wear, your guitar will go out of tune when you use the whammy bar. When this happens, replace the springs; change them all at once so they wear evenly. The springs just hook onto little hooks, and with a little tugging and the aid of pliers, you can pop them off and on in no time. You can even tighten the screws on the plate (called the claw) where the hooks attach, increasing the spring tension. Don't worry — these springs don't go sproingggg and hit you in the eye or go flying off across the room.
Some people like a loose bridge (which is more responsive but goes out of tune more easily) and some like a tight bridge:
If you like a stiff bridge that stays in tune (and who doesn't!) and you only occasionally use the whammy bar, go for a stiff bridge setup. The more springs, the tighter the bridge; so if you have a two-spring setup, consider switching to a three-spring setup.
If you like to use the bar and you're willing to trade a little tuning trouble for having a bridge with a lot of play, consider a looser setup. Guitarists who like to create ambient music (atmospheric music without a defined melody) often do a lot of dips and pulls on the bar, and so prefer flexible bridges.
Crackling guitar controls
Dust and rust (oxidation) pose a potential threat to any electronic connection, and your guitar is no exception. If your pickup selector switch or volume and tone knobs start to make crackling or popping noises through your speaker whenever you're plugged in, or if the signal is weak, inconsistent, or cuts out altogether when the switch and knobs are in certain positions, some foreign matter (however minute) has probably lodged itself in your controls.
Vigorously flick the switch and turn the knobs back and forth around the trouble spot to work out the dust or rub off the little bit of corrosion that may be causing the problem. You may need to perform this action several times on each knob, in different places in the knob's travel. If turning the knobs doesn't do the trick, you may need a repairperson to give your pots (short for potentiometer, the variable resistors on your volume and tone controls) a thorough cleaning.
Loose guitar jacks
On electric guitars, you do a lot of plugging and unplugging of your cable, and these actions can eventually loosen the output jack, causing a crackling sound through the speaker. This crackling indicates a disconnected ground wire. Here's the fix: Take off the jack plate or pick guard and locate the detached wire causing the problem.
If you're handy with a soldering iron, attach the broken wire back to its original lug, and you're done. You may even feel like a real electrician.
If you're not handy, have a friend who is do the job or take the instrument in to the shop.
Replacement pickups
Replacing your pickups can seem like a daunting task, but it's really a very simple one. Often, the best way to change your sound (assuming that you like the way your guitar plays and looks) is to substitute replacement pickups for the originals — especially if the originals weren't too good to begin with. Here's how:
Purchase pickups of the same size and type as the originals.
Doing so ensures that they fit into the existing holes and hook up the same way electrically.
Connect and solder two or three wires.
Clear directions come with the new pickups. Follow them!
Seat the pickups in the cavities.
You're not dealing with high-voltage electricity either, so you can't hurt yourself or the electronics if you wire something backward.
Again, however, if you don't feel comfortable doing the job yourself, enlist the aid of a handy friend or take your guitar to a repairperson.
Changing your pickups is like changing your car's oil. You can do the job yourself and save money, but you may choose not to because of the hassle.