Get lessons. You can learn on your own or online but seriously, take them for 1 or 2 years just to help get your footing. I took lessons for 6 years. During that time, I found it helpful to learn songs that challenged me but didn't stump me. It's like anything, push your limits but don't break yourself. If you learn a fairly difficult song for yourself, you'll learn the techniques that song may use. So my number 1 advice is actually seek lessons out, even for a year or two.
For discussion, I got my first guitar when I was 9. I can't even remember what it was, it was an acoustic oscar schmidt if I had to guess. I took lessons at age 10 until 16. I started learning acoustic until age 13. At age 12 I started learning electric, and I was getting into metalcore and such.
At one point when I was 16, I wanted to learn a song with my guitar teacher. He couldn't find a tab so he said "no problem, we'll learn it by ear". When I showed it to him, though, he couldn't pick out what they were playing and figure it out. I could picture in my head what to play so I took a shot at it and after about 30 minutes I had learnt about half the song. That's when he said I no longer need lessons and could fend for myself, and I've been figuring out techniques and such on my own ever since. I learn new stuff all the time as the obstacle comes at me, say learning pinch harmonics a couple years ago, or mastering sweep picking.
With that anecdote, I'll just say again, TAKE LESSONS. It's a lot easier to get that footing where you can then just teach yourself.