I always adjusted them so the iron hit my ankle bone :)
Of course, that changes depending on who I ride. If I'm on a really big horse, then a lot of times I'll drop them one hole. On ponies, I sometimes raise them a hole [i'm 5'8" so I gotta raise it to keep my leg on!] I ride with relatively short stirrups to begin with though, so I don't like to raise them at all.