Since you spend most of your time walking, blisters are really worth avoiding. First use boots that have been worn in if possible. Test your boots by carrying a pack up and down hills - along level ground there is far less stress on your feet. Don’t go with new boots on a long walk.
Normally you can feel a blister developing - some rubbing, or a hot spot, or a localised pain. Stop and investigate, even if it occurs during the first 5 minutes, or just in sight of the top of the hill; immediate action is best. The trick is to detect the symptoms before the blister develops. Put tape on or investigate what may causing the problem.
Blister Treatment - If you develop a blister then there are several approaches. If it is not painful then perhaps surround it (not cover it) with some light padding, e.g. moleskin, and see how it feels. If it is painful and causing problems then pierce it - clean the skin and sterilise the needle; holding the needle slightly above a candle or match flame for a second or two is effective. Do not cut away the blister skin until after a few days when it is dried out and no more use for protecting the delicate skin underneath. You can put protective tape over the top with some cotton wool to protect the blister, and some people even put the tape straight over the blister, with no protection.
If you have had a previous history of blisters or think that you are likely to get them take preventative action first! Use moleskin, a strong waterproof zinc-oxide tape or similar, and tape up troublesome areas first. Tape before you take your first step and be religious about checking, and replacing, the tape.