1. Learn how to tune your guitar very well. Most beginners have a terrible ear for tuning, so their guitar is always slightly out of tune. Always tune it before playing, and spend time trying to make it close to perfect as you can. It makes a huge difference.
2. Watch a shitload of Phil X videos on youtube. [link]http://www.youtube.com/user/frettedamericana[/link] Everything he does is awesome, but he's a very sloppy player sometimes. He'll teach you that even professionals can suck sometimes. It'll keep you from getting discouraged. He also demonstrates about a billion different vintage guitars, so you can learn the differences between guitars and gain an appreciation for sweet vintage stuff.
3. Learn all of the basic chords, and learn different forms of them. The basic cowboy chords translate very well into power chords and barre chords. Practice switching them as smoothly as possible.
4. Don't immediately try to play fast. You can't, period. It takes lots of practice, so if you want to play fast licks, use a metronome and start slowly. Speed it up as you become comfortable.
5. Learn classic rock songs. Ignore everything else for the time being. Classic rock is pretty basic. It'll help with your rhythm playing and lead playing all at the same time. Learn to play AC/DC, Boston, Bad Company, The Who, Black Sabbath, etc. (guitar-heavy classic rock). Even if it isn't your favorite genre, you'll probably learn more from playing classic rock than anything else. You'll learn blues licks, the basic chords, power chords, pedal tones, filler licks, blues soloing, and all sorts of other stuff.
6. Don't buy super fancy equipment yet. You don't need it, and it won't make you sound any better yet. Don't spend more than a couple hundred dollars on a practice amp, and don't spend more than $350 on a guitar yet. Line 6 makes decent practice amps for beginners that can be played at bedroom volumes. They aren't by any means great professional rigs (I will ignore all posts from other users who think they're great because so-and-so uses Line 6 products...I know that SOME people play them professionally, but they are FAAAAAAAR from the same rigs that amateur guitarists can buy on the market), but they are great practice amps with all sorts of neat settings for you to mess with. Fenders line of Mexican guitars are good for beginners, and a lot of used Epiphones are great, too (the Korean ones, not the recently built Chinese ones.) Also, ALWAYS play the exact guitar you want to buy before buying it. Don't order something online...go to a store or browse around on craigslist, play some guitars, and find the RIGHT ONE.
7. Alternate pick EVERYTHING. There are some cases in which alternate picking is not necessary, but if you learn to do it now, EVERYTHING will be easier later.
8. Play every day. Set a practice regimen for yourself, and follow it.
9. Find other people to play with, preferably at least a drummer. It'll help a lot.
10. Treat your guitar with respect. Clean it regularly, change the strings as frequently as necessary (depending on how often you play), and don't do stupid shit like guitar flips.
For the record, I've been playing guitar for twelve years. These practices helped ME, so the may not be perfect for everybody. To each their own.