What is the best way to prune Bougainvillea shrubs

With heavy gloves and protection for your arms! The thorns are horrible. In my experience, bougainvillea is very hardy. I just cut into the shape I want and it has never suffered or died from it. We had one that climbed into a tree because we neglected to prune it. We had a terrible time getting it out of the tree. We cut the branches we could reach, but that left branches way up in the treetops. We had dead bougainvillea branches falling from the tree for years. (we didn't want to climb up to pull them out.)

I forgot to say that after you prune, the blossoms will come back pretty quickly.