The best advice for developing speed is obvious, but perhaps it isn't quite that simple.
Obvious answer is sheer repetition. In developing any discipline you either are willing to do the required repetions or you are not. If you are not willing to pay the price(of time, effort, consistency) then forget it...you aren't going to get very far. Many guitarists wonder why their technique isn't getting better when, in fact, they only practice technique for a few minutes every day. It takes a lot more than that!

On the other hand, you also need to practice with good form. This is where a teacher can definitely come in handy.