Blisters occur from injury to the skin from friction.
If you can take the pressure off of your blister by avoiding contact or surrounding it with a donut bandage than you should do so. If your blister is someplace where this is impossible than you are better off draining it than having it tear or rupture. The best way to drain them is to thoroughly clean the area then lance the blister with a sterilized needle sideways from an edge and slowly squeeze out the pus. You may need to lance the blister in a few places to completely drain it. Do not peel the skin off of your drained blister. It continues to protect the injured area so just bandage over it with a bandage and neosporin to prevent pain and infection.
If you continue to reinjure the same area you will develop a callouse to protect the area.
DO NOT POP IT. That will leave dead skin that will rip and tear and hurt like f*ck. Wear comfortable shoes, and just leave the blister. Eventually it'll just dry up and go away.
use a blister plaster. For me popping works good, it doesn't hurt at all if you do it good.