The most efficient way to learn guitar I suppose would be to hire a teacher, but that, IMO, is like cutting the corners - meaning you don't learn everything you would by yourself, all the fine points - as well as limiting the creativity of the whole deal. Other than a teacher, you've got to listen to tunes all the time you're not practicing for your subconcious to learn. Styles will rub off on you, as well as riff ideas, so becareful not to limit yourself to one or two artists in particular (one or two styles for sure).
Other than that, the more you play guitar, the better you'll be! That's all I can say: Listen as much as you practice, and practice all the time.