First Steps
One technique I use to establish a good structure for practicing is taking a lesson and emulating a practice session with the time allotted. That often means some sort of a thorough warmup, working out of a book(s), working on a real-world song, and working on some chords. If we have thirty minutes, we can divide each of those sections into roughly seven minutes each.
During the course of a lesson, I refer to the previous weeks' lesson and jot down notes for the week ahead. Sometimes its good to spend an entire practice session on just one or two areas, sometimes only one, sometimes a little of all areas.
Like a lot of this stuff, there is no one technique that works for everyone. I'm also keenly aware that guitar isn't the only thing in a person's life (that one took me a while!), so some weeks might beget hours of practice, others very little. One thing to keep in mind is that guitar IS life. In many ways, the way you approach the instrument is a great mirror for the way you approach other facets of your life!