Here are some guitar practice tips from Joe Satriani, by way of Guitar World that I found useful:
1) Don’t spend more than an hour on any one thing.
The brain can only hold so much new information before it says “enough.” Scientists have studied the changes that occur to the brain when a person learns something new. They’ve found it takes a while for the brain to recover before it can process new information. So limit yourself to one hour a day on anything that is new or especially challenging.
2) Keep it fun.
This ties in with tip No. 1. Practicing isn’t always fun, but there are ways to lessen the boredom. When I was a kid, I’d get up and practice guitar for an hour before school, and during that hour I’d do all the boring stuff just to get it over with. That way I could come home, do my homework and then jam with my friends.
3) Find the note everywhere.
As an exercise, learn how to locate the note E everywhere, on every string. Once you’ve mastered that, go on to B, and then the other notes. Once you’ve demystified the placement of notes, you’ll be amazed at how freely you’ll be able to move about the neck.
4) Stay in tune.
When you practice, you’re sending musical messages to your ears and your brain. Even if you don’t realize you’re out of tune, the brain does, and it sends a little message back; “This doesn’t sound good. Stop practicing.” So buy a tuner, use it and stay in tune. You’ll practice longer.
5) Run through every chord you know.
It seems silly, but if your fingers don’t go to a certain place it’s because you haven’t challenged them. One day, when I was a teenager, I decided that I was going to learn every chord in a Joe Pass chord book I had. I worked on it every day; there’s no substitute for bonehead repetition. The great thing is, once you get used to this exercise, you’ll literally force your fingers to go from chord to chord to chord—chords that have no relation to each other—and great things can come from that.