Don Firth, I agree. Learning more is always an advantage and never a disadvantage. I've always found music theory to be very satisfying and interesting in itself, apart from its usefulness for playing. My problem was always that my playing always lagged behind my knowledge of music. Now I'm pushing 50 but it's starting to catch up. Better late than never. The breakthrough for me was finally sitting down and trying to learn to play by ear: something that was definitely discouraged in the music teaching I received as a child.

Don Meixner, I recommend the major scales all over the guitar, on single strings and in all the positions (that you can play comfortably). The major scales are, in my opinion, the most important exercise of all and I go back to them very frequently. I have more to say on the subject, but the (virtual) whistle is about to blow and I have to start work.