hey dudes, good luck with the playing!
Once you got a guitar (preferably acoustic, I found even the big strings were too painful after a few minutes when I started off) I would say you should hang out with some buds who play. 'Cos its so hard being motivated to play when it sounds crap all the time! At least with other people you can hear what it might sound like!
I think the quickest way to get the feeling of actually getting somewhere, so you stick at it, would be to learn a few chords, so you can at least play some songs. Example (thick to thin strings left to right)
A 002220
D x00232 (x means dont play this string)
E 022100
now you have yourself enough chords to jam out something in a rock and roll number, at least! Or you could learn power chords, and shift them for the chords. Power chords are used a lot in heavy rock i.e. all the bits in Smells Like Team Spirit (below) You dont use open strings so you can move the whole shape of the chord up or down to go higher or lower:
G5 D5 C5 E5
3 5 5 x x x => 10 12 12 x x x => 8 10 10 x x x => 12 14 14 x x x
note this can also be played, by moving the shape up:
G5 D5 C5 E5
3 5 5 x x x => x 3 5 5 x x => x 1 1 3 x x => x 5 5 7 x x x
God, theres loadsa different ways to go about it. I think learning normal chords as well (i.e. C, D, Am, Em, F, G etc etc) is good because you can try more songs.
Anyway, my tips would be:
1. Learn to tune it. Get a cheap digital tuner. You're going to have enough trouble getting a decent sound!
2. Make sure you are holding the thing right.
3. Play up and down strokes. I played a couple of years on downstokes only, and it took me ages to play properly!
4. Play it clean at the beginning of a jam, then whack up the volume and the so you are left with a satisfactory feeling when you finish playing and you want to come back for more.
5. Get a folder of stuff you are working on, so you have an idea what you're up to.
This guy has good advice.
http://tedvieira.com/index.html
Good luck