There are 2 main causes for blisters. a) Ill fitting boots, and b) your skating technique. So the first thing to do is to check that your boots fit properly. If they are one size too big, that will cause blisters. Next, heat mold your boots. Now let's work on your technique. If you push backwards with your toes rather than to the side with your heels, your ankle will no longer be in the right area of the boot and it will cause pain and blisters. The first thing you need to do if you have blisters is to let your feet heal because you won't know if this fix will help if you still have pain. Once your feet heal, try this. When you skate, hold your toes up against the top of the boot. It will make it very hard to toe push. Now concentrate on pushing to the side and with your heel. If someone can video you it would be even better. In 90% of heel blister cases, this solves the problem. Once pushing to the side with your heels becomes second nature, you can forget about lifting your toes up in the boot.