Now onto actual guitar tips!

You still want to learn to play guitar? You brave souls.

It's dangerous to go alone. Take this! (Pulls out an extra set of strings and a handful of picks. Also, awesome Zelda reference!)

1) Learn on acoustic. I learned on electric and it's done well for me, but learning on an acoustic guitar gives you a more rhythmic feel. It all starts with knowing how to strum simple chords. Besides, acoustic strings are thicker and have higher action, so it will make your hands stronger and electric guitar playing will come that much easier.
2) Never underestimate the power of the chord. Keeping rhythm and playing chords are both important as a guitar player. Since I learned on electric, I am more comfortable playing leads than I am with chords and rhythms, which are the bulk of what you will probably be playing. It might not sound as cool, but it's essential. Make sure you know how to play C, D, E, G, and A chord shapes as well as D minor, E minor, and A minor.
http://en.wikipedia.org/wiki/Open_chord
3) Barre chords are your friends. Once you know the basic E, A, and D shapes and the parallel minor forms, you can use the same shapes (Mostly E and A, but the first three notes of a D chord in barre form can act as a power chord) in any key by moving them up and down the neck and barring the strings with your first (index) finger. The barre acts as the nut, so the bottom note of what you play should be the root of the chord. It's much easier to explain on Tabulature or a chord chart.
http://en.wikipedia.org/wiki/Barre_chord
4) Having trouble with barre chords? Can't stretch out that first finger? Use a capo. It acts as a nut and is used to play songs in different keys higher up on the neck. Unfortunately, if you want to travel anywhere on the neck, work at those barre chords.
5) Turn on the power chords. These chords are really simple. They only involve the root and the fifth of the chord. Try making a barre chord and only using two fingers and striking the bottom two notes of the chord. It sounds huge! That is the secret to playing rock and roll rhythm guitar and travelling up and down the neck quickly. They can also be played inverted with the fifth on the bottom, or played with three notes by adding a root on top of the fifth (Root, fifth, root) or to sound really heavy, even playing with four notes by adding a fifth on the bottom (Fifth, root, fifth, root)! Reccomended for playing on the sixth and fifth strings.
http://en.wikipedia.org/wiki/Power_chord
6) Watch your fretting. I learned this tip recently actually, I always used to fret in the middle of the wooden space between frets. However, I learned that if your finger is in the direct middle of the wood or closer to the lower fret or the nut, the pitch could waiver a little. Press your finger up close to the metal fret wire that you are actually fretting for the most accurate pitch and tone.
http://en.wikipedia.org/wiki/Fret
http://www.youtube.com/watch?v=SpuxG8xYu5k
7) Get a grip. The best fretting hand grip for when you're playing guitar, especially for chording and especially on acoustic and classical guitar is one where your fingers are arched (except the first finger when barring) and the thumb is at the back of the neck. Also, you should lead with the thumb while shifting chord positions. I learned that from playing classical guitar; when you're shifting positions and the thumb is dragging behind, it flattens out your fingers and makes it hard to fret difficult chords. Try leading with your elbow as well. However, old habits die hard and a lot of people, myself included, do the baseball bat grip let their thumb wrap around the guitar, and to be honest, it works for bending strings and you can even fret bottom notes with your thumb! Even the best guitar players can have imperfect technique, but I'd recommend learning good technique before you fall into bad habits, then developing your own style.
http://www.dummies.com/how-to/content/id-87604.html
8) No deathgrips! Unless you want to damage the fret wire, the fretboard, or your fingers, don't press too hard, just enough that you're audibly pressing down the notes.