I adore scrappy quilts so I usually get 1/2 to 1 yard pieces. I love remnants!
If it's something I will want to use for solid borders, I get 2.5 yards because I don't like to piece borders if I can avoid it.
If it's something I will use for quilt backing; I get 2.5 yards if it's wide, or 5.5 yards if it's not. That gives me plenty of backing plus leftovers. I love cutting long strips off of leftover wide backing to use as binding on my next quilt; I dislike seams in my binding so if I can bind a whole quilt with just 4 separate pieces of fabric I'm a happy camper.