Im with IDP on this one.
If you're out running and you get a blister, keep going and ignore it. There is a lovely, palpable sense of "aaaaah" when it finally pops of its own accord.
If you find one at the end of the day, I just pop the thing and ignore it from then on, though there have been a fair few times when I've only noticed that Ive had a blister by inspecting my feet in the shower, only to find a patch of skin coming off where a blister has come, been and healed. Maybe Ive just got a bit too used to them. I dunno.
For what its worth, when I ran in mudroc 260s and they created the worst blisters known to man on my heels, I just ended up a)hammering the crap out of the heel cups and b) wearing pre-emptive compeed on my heels (best when heated up on a cup of tea before applying) that seemed to sort them out.
then again, each to their own.