Oxylers is great for The Other Stage, Silver Hayes and John Peel.
Big Ground / Kidney mead is great for the Pyramid
Pennard Hill is my personal favourite. it's closer to Arcadia, South East Corner and Other stage. Park Home is a good alternative though
It really depends on where you're likely to spend most of your time, there's not too much difference in atmosphere between Oxylers and Pennard (been a while since I was in Oxylers though!) but from what I remember, Big Ground / Kidney was a little bit more laid back.
And yep, if you want to stand a good chance of getting a space in any of the above, make sure you approach Glastonbury from the right direction so you get in the queue for the Gate closest to where you want to go (Gate D for Pennard, Park Home, Oxlyers. Gate A for Kidney / Big ground) and get comfortable for the next 8 hours!