In reply to Seldom Seen Slim:
Pre-emptive padding is a good bet. I used to get horrendous blisters on the back of my heel until I started doing this. Have you ever used Compeed? It's basically like adding an extra layer of skin, and if properly applied (warm it in your hands for a minute or two, do your best to avoid bubbles / creases) it should help a lot. A bit of climbing tape on top can help ensure it stays in place. Be careful when taking it off, it's a strong adhesive - if you put it on top of a blister (and ideally it won't get to that stage), you'll probably take the top of the blister off with it. Remove in the shower ideally.
Combine this with some talcum powder - keep your feet nice and dry, and that's half the battle won. I've seen people put powder inside the sock before putting it on, and that works a treat.
Lastly, if you feel a hot spot developing, stop if at all possible. Remove the sock, replace it with a fresh, dry one if you can, and give your feet a minute or two to air. Re-talc your feet at that point.
Ultimately, it's about finding 'the perfect boot' that fits YOUR feet. Best of luck!