Fret Check :

If you want a fret-checker and can't make it for yourself...
Click on the payment logo and You'll get one for $19.95 everything included.
Make sure to fill out your address and give an exact measurement of the size you want.
A great way to check the neck and frets on any guitar is to go to your local hardware store (home depot) and get a piece of aluminum rectangular bar 1/4 inch by 1 inch.
The 1/4 inch side of this bar is absolutely perfectly straight. It usually comes in an eight foot length, so either cut it there or you'll have to buy the whole piece (make sure to sand the cut edge)... the length you'll need is 2 and 3/4 inches (almost three inches) or whatever distance just overspans frets 1, 2 and 3 on your guitar. Now you can place it on the frets between the strings like the side view (shown in picture) and find out everything about the frets and neck.
1 : If you slide it up the fret board and it goes without rocking or hitting the next fret, everything is fine. ("rocking" means if you pushed down right above frets 1 or 3 it will be able to move)
2: If the checkbar rocks, it means the center fret (2) is a little high or one of the others is a little low, so that means go to the next frets 2, 3 and 4, if it still rocks all the way along, it means the neck is curved backwards away from the front and you can release the truss rod a little. The truss rod gives opposite tension on the neck from the strings. The strings try to pull the neck forward, the truss rod will pull it back if you tighten it.
3: If, as you're sliding, the checkbar will noticeably hit the next fret... it means either the next fret is high or the neck is curved forward. To find out which you just keep running it along and checking what happens at every fret position. If the neck is curved forward... you can tighten the truss rod a little. If you understand the way this works you'll be able to tell exactly what's going on with your neck and frets and give it a precise fix. You can also keep it in your pocket or drill a hole through it and keep it on your key ring and give a quick check to any guitar you're thinking of buying in a music store.
Picture legend... it's a side view. Checkbar is grey, string is blue, frets are black, neck is brown.

Truss Rod :
If you've checked your frets and decided your neck is curved forward, it means you can tighten the truss rod a little. To do that you give it clockwise turns. A good thing to know is after you've tightened or loosened the truss rod... it will either put more tension on the neck or release some. This will enable you to immediately straighten a curved neck, but after about a week or two the neck (made of wood) conforms to the new shape but the tension is still there and it might cause the neck to go further in adjustment then you wanted. My thinking is... if you give the rod three 1/8 turns... it will go an additional 1/8's (worth of) turn on it's own in about a week. Does this mean you should back it off 1/8 turn? No... because if you back it off the 1/8 turn and the neck goes back to perfectly straight, it might go an additional slight bit in the next week. The best thing to do is count the number of turns till perfect then maybe back it off a little and let it go into perfect by itself then only make very slight adjustments thereafter.
Where is the truss rod? It's in the neck but the adjustment nut or allen is either in the sound hole right at the base of the neck or under the plastic triangle (usually) right at the top of the nut. you can only give it for instance 1/8 turns because there is no way to make a 360 without going through the wood or busting the strings... yes, you should leave your strings on and make sure you are tuned to correct pitch while doing it.
Also, if you plan on storing a guitar: it's a good bet to leave the strings on it or else there will be no forward pull (tension) from the strings and the truss rod will warp/bend the neck backwards (over a period of time). And then when you decide to put strings back on it someday it won't come back to normal for about a week or two. But since you didn't know about the one week thing... you've tried to adjust it immediately and inadvertently made it wrong (you'll find out in a week) .

Playing Tip :
Make sure your right hand (or the one you hold a pick with) is never balled up in a fist like shape when you're playing. Your hand should be in a shape like it is when you make the O.K. hand signal, with the thumb and first finger in a circular shape holding the pick, and fingers 2, 3 and 4 just about straight (especially when strumming). If you're picking individual notes you can also use your pinky as a support or stabilizer by resting/holding the tip of it against the guitar body. You will/can be much more articulate with your playing this way. The right hand in a fist is just bad.

Song Writing Tip :
There's nothing wrong with writing a song that has only 3 basic chords ( here's one I made up using only E, F, G chords and some kind of India scale... india_rumpus.mp3 ), but if you really want something creative and unique... try to think of something in your head while driving or at work or just sitting around etc. then remember the way it goes or write it down in a way you'll be able to remember it later (they might be chords you've never used or heard before, but that doesn't matter). Then when you actually have a guitar in your hands and can piece together (figure out) what the correct chords for the song were, you might just have a hit.

Playing Tip :
| index=1 | middle=2 | ring=3 | pinky=4 |
The best way to play a chord is however you feel most comfortable with, although I always try to set myself up for an easy change to the next chord like...
Playing a "G" with fingers 3,2,4 enables an almost immediate transfer to "C" with fingers 3,2,1
Play an "A" with fingers 2,3,4 if you're going to an "E" 2,3,1, next, always try to set yourself up. Examples below...
index=1 middle=2 ring=3 pinky=4

G fr-open

C fr-open
x C E G C E

A fr-open
x A E A C# E

E fr-open
E B E G# B E