Ugh, blisters are no fun!
I do marathons and triathlons, and I work in a job where I have to wear heels/dress shoes often. There's one product that saves my feet from turning into hamburger, and it is beyond awesome. It's called Bodyglide (yeah, I know, silly name) but trust me, it saves your feet (or thighs, or armpits, or anywhere else you may have blisters/chaffing). It's sweatproof, waterproof, odorless and colorless. I swipe a little on and off I go.
http://www.rei.com/product/745879
That's the small size, it's tiny enough to be TSA (and purse!) safe, but there's another that comes in a larger size and it looks like a tube of deodorant (DO NOT CONFUSE THE TWO!). A little goes a long way!