Note: Listed below are just some ideas of how you can adjust your truss rod and other guitar maintenance techniques. There can be more technical ways to do these tasks as well. Always consult a professional guitar technician if you have any questions about guitar setup and adjustments.
One easy way to quickly check and see if you have a bow in your guitar neck is to pick up your guitar and hold the body of the guitar up to a light. Take a look from the body up to the neck and try to see how your neck is sitting. Usually if you hold it up to a light source you will notice if your guitar neck is bowed or not. This is not the schooled method of checking neck bow, but its and easy eyeball method. Most guitars have a neck adjuster at the top of the guitar (the headstock of the guitar). It may be underneath a cover or there may be a hole near the center of the nut. Inside this hole is the end of the truss rod where you can adjust it. There are also some guitars that have bullet truss rod adjusters at the headstock. Depending on the type of guitar, you can adjust the truss rod that is in the center of your necks headstock with a tool (truss rod adjuster - wrench like tool) usually given to you when you bought the guitar. Usually a truss rod adjuster is needed for this task. Ask your guitar store tech to see which truss rod adjuster tool will work for your brand of guitar. Try adjusting the truss rod to improve bow of the neck. A little bow upward is ok. Usually, tightening the truss rod gives a straighter neck while loosening the truss rod should give a little more bow to the neck. The adjustment you make depends on your guitar and how you would like your guitar neck adjustments. Find Truss Rod Wrenches and Covers for your guitar as well.
If you do not see a truss rod adjustment at the headstock it is most likely at the other end or butt of the neck. Note: It's usually only at the butt of the neck on vintage guitars or reissue type guitars. This is not the norm for more modern guitars. See above for modern type guitars. On some styles of guitars it is possible to adjust without taking the neck off of the guitar. But in most cases you will have to unbolt the neck from its neck pocket to adjust a vintage guitar neck. If you would like to save your current strings, you can put a capo on the neck to save the strings. Sometimes you will just need to take off the strings to adjust the neck. This is a trial and error process, but once your neck is adjusted properly, you will no doubt get a better sound and feel out of your guitar. Try small quarter turns of the nut to see what kind of response your getting. To make your guitar neck straighter try tightening the truss rod. Loosen the truss rod to give more of a bow to the neck. The adjustment depends upon your style of play and how you like your string height on your guitar.
Raising the pickup height closer to the strings should result in a little better tone for you guitar. Visa versa lowering the pickup should give a lighter tone to your instrument. All you usually need is a little screwdriver to perform this modification. This is a trial and error process so keep your amp handy to test the sound at different positions. To do this adjust the screws on either side of your pickups. Tightening the screws should lower the pickup while loosening should raise the pickup. Be sure not to raise the pickups to close to the strings or you may cause the pickup to sound out of phase. And be sure to adjust the screws evenly on each side so that your getting the same response from all the strings. To get a balance of sound you may have to angle the pickups a little away from the lower heavier stings. Again, this is a trial and error process but may give your guitar a different tone. For more detailed info on Pickup Height Adjustment - Click Here
Note: If your guitar has a Faded Finish (ex: Gibson SG Faded) the polishing techniques below will NOT work since your guitar technically does not have a lacquered finish).
For a lacquered finished guitar body, find a nice guitar polish at your local music store along with a chamois polishing cloth. Some guitarists use windex on their guitars, but I have not tried this technique myself. Basically, you should polish only the major surfaces of your guitar avoiding the guitar parts like the bridge or tuners. Spray a little on your cloth and polish away. Also, you may not want to polish your guitar neck unless it is lacquered because this could hurt the wood on your guitar neck. Guitar Polish & Kits can help to keep your guitar clean and maintained.
Some guitarists prefer oil on there Non-Lacquered guitar necks. Oiled necks tend to have a nice feel for guitarists. For example, the Eddie Van Halen Wolfgang Guitars would come standard with a non lacquered oiled guitar neck. You can find an oil you would prefer to oil your guitar necks at many guitar stores. Some oil types include lemon oil, tung oil, or tinted oils. Once you find and oil your satisfied with do a small test on an area of the neck that is not exposed, maybe the butt end of the neck. Check to see if this will be the look and feel that you want on your guitar neck before you oil the whole neck. Basically take your cloth or chamois and apply light coats of oil to your guitar neck. If you get some oil on the frets just take a dry cloth and wipe off the frets. Of course, read the instructions on any oil that you purchase. Give the oil some time to dry and you have a nicely oiled neck. If your guitar neck is rather dry it may soak up the first coat quickly, so if this is the case you may have to apply another coat of oil once the first coat dries. Guitar Lemon Oil May help when oiling your guitar neck.
The string action can be raised or lowered by adjusting the bridge. If you don't feel comfortable adjusting the bridge yourself try your local guitar dealer. They usually employ technicians to help with guitar modification. Basically to raise or lower your bridge adjust the screws on both sides of the bridge. This is another trial and error process so adjust the bridge a little at a time and test. If you adjust the bridge to low your guitar may fret out. This means that the strings are adjusted to low and give false tones when certain notes are depressed on the fretboard. Also if you go to high your action may make it more difficult to play chords on your guitar. So a little Guitar Bridge adjustment can go a long way.
Some pickups come equipped with adjustable pole pieces. They are usually either screw type or hex nut type pole pieces. Some guitarists feel that adjusting the pole pieces so that they are a little closer to the strings give a fatter of better tone. Others say you should not adjust them. So it's up to you whether you want to try this task. Check out your pole pieces on your pickup and see if they are adjustable, and use either a small screwdriver or hex wrench to adjust. Adjust and test your instrument with small adjustments. Don't adjust to close to the strings or you'll get false tones. For more detailed info on Adjustable Pole Pieces click here.
Sometimes your Guitar Tuning Pegs may feel loose and unstable. An adjustment may help out. The next time you restring your guitar take a small screwdriver and tighten up the screws on your tuning pegs on your guitar headstock so they are snug. Sometimes with constant string tension these pegs can loosen over time. Be fairly gentle with these adjustments because some tuners can damage easily. This tuner adjustment should help your tuning pegs keep the tension on the strings properly.
The nut is the plastic or bone piece located near the headstock that holds your strings in place. If you have a guitar with a tremelo or whammy bar that goes out of tune when you use the trem, try oiling the nut. Pull the string up a little and put a drop of oil in each string slot of the nut. Try not to get oil on the fretboard or headstock. OIling the nut should help the strings slide through the nut with less friction when the tremelo is used. Remember as always when using oil a little goes a long way.
Strap Locks are a great feature to add to your guitar. Strap Locks basically lock in the strap of your guitar so it doesn't fall and get damaged while your playing it. I can't tell you how many times I almost dropped my guitar before buying strap locks. If your buying more expensive guitars this is a must have option. I've found that Schaller Guitar Strap Locks and Buttons work great but others brands will do the trick. Basically just unscrew the old strap buttons off you guitar and screw in the new strap lock buttons that you buy. You'll also have to add the locking pieces of the strap lock to you strap itself. Screw those pieces together, and you should be able to snap in or strap lock your guitar. A wrench and screwdriver may be needed to add this strap lock option to your guitar and strap.
*These are some ideas to help with guitar setup. Always unplug your guitar from your amplifier before making any adjustment to guitar electronics. If you are a novice it may be a good idea to get a guitar setup done by a professional. Most music stores have in house technicians that can help with this process.