Oh forgot to say actually learn music you like. You'll get much more of buzz learning say hey joe (if that's what your into) than greensleeves.
This is good advice. But sometimes, if you've been playing for a while, you forget what it's like the first time you pick up a guitar. If it has rusty old strings on it, how do you change them? How do you tune it? How do you hold a pick (assuming you'll be flat picking rather than finger picking)? And never mind what do you start learning. Justin's site, above, will show you all this if you don't have a mate around who can get you started with this stuff.
Already, it looks like there's conflicting advice here, but not really. I still say get those open chords down. But this doesn't mean you can't try other things as well. Another thing to learn early on, is how to read guitar tab, which is essentially diagrams of the fretboard that show you exactly where to put your fingers on each string for any particular thing you are trying to learn, whether it be a chord or a whole tune. It's simple, and is one very useful tool if not figuring out from a video, or just by ear if a little more advanced.
So once you understand tab, then you can choose a tune you like, find the tab, find a video tutorial for it, and combine the two to learn how to play that tune. Mick's suggestion of Floyd's "Wish You Were Here" is a good one, nice and easy. "House of the Rising Sun" is good for learning to pick individual strings cleanly whilst fretting basic chords (arpeggios). A favourite tune with a simple one-line lick/riff and a couple of easy chords would help to keep you interested. Scales can come a bit later in my view, once you're comfortable with one or two basics, although they too can help with your picking and fretting practice - very boring running up and down them though, so do some other stuff to keep it enjoyable too.
So probably, have a few different things to be working on for a bit of variation, but you have to start somewhere, and, once the guitar is tuned and ready to play, those open chords would be the very first thing I would teach you if it was down to me.