I do a small ribbing for about two inches, either a K1, P1, or lately I've been doing a five-stitch rib: P1, K2, P1, K1
Then I usually switch to a larger rib for the leg of the sock...something that will give a pattern but at the same time provide snugness. If I do a non-ribbed leg, I often decrease some stitches to increase the stay-up factor. I HATE saggy socks!!!!