good fitting shoes or boots and two pairs of socks are good at preventing blisters, but you also need to be aware of any hospots on your feet, its those that generally become blisters. Once had a blister that completely covered my big toe while up a welsh mountain, freezing cold and soaked, it had already buirst by the time I noticed it but I got a compeed on it and was able t walk back again and continue walking without much pain for the rest of the week. They promote healing too.