I alway stand when I rehearse, and I used to wear my guitar quite low, but I found it real hard to play lead, and I couldn't play barre chordes very well. Now I wear it up around my stomach. Its become a whole lot easyer. What I do is pick a peice of really fast music, and if I can play it without straining my wrist while standing, I know my strap is where I want it.
And God said, 'Let there be rock!'
-And it was good