There is no reason not to take lessons in the beginning. The key is to take what you learn and use that as the building blocks for exploring how to make music, as opposed to some people who rely upon what they learned like a crutch. Think about it, you can either pick up some of this information on your own as you go (key, chord structure, rhythm, strumming technique, etc) or have someone give you this information up front. Failing to have a clue about where to start is what keeps so many guitars in people's closets unplayed. That said, these things are helpful-
Proper left hand and right hand technique- Learn how to hold a pick, and how to use your left hand. Do string exercises, it helps.
Learn the notes on the neck - Figuring out what key a song is in is just plain valuable.
Learn some chords - Just the basics, and then start experimenting around with different chord structures.
Tempo/Timing - spend some time playing to a metronome. There is nothing more annoying than a guitar player with no sense of rhythm. Believe me, there are TONS of them out there, and they're all useless in a band structure.
Learn different styles- This one is touchy for a lot of people. Years and years ago, when I wanted to learn how to play, I went to my bass teacher to learn how to play like this once popular band called "Metallica". He hated said band, and instead insisted if I learned how to play jazz, blues, rock, reggae, bossa, folk, metal, etc. I would be a far better player for it. He was right.
Finally, outside of lessons find people to play with who are better than you, no matter what style they play, and jam with them. I learned most of what I know about writing and coming up with stuff by playing with people who smoked me and watching their technique and listening to their ideas.