Nature's signal to me that it is safe to prune is after the blooming of the forsythia in early spring. I use sharp pruners and sterilize in a weak bleach and water solution, repeating as I move from bush to bush. My cuts are made at a sharp angle for better healing. My aim is to remove at ground level all dead canes, all canes pencil width or smaller, and the weaker of two canes that are rubbing together. When I finish pruning a bush, I will have only three to five superior canes.
Fewer canes mean fewer flowers, but larger and better developed ones.
I prune climbing roses differently. Because old canes on climbers produce more abundantly than new canes, I remove old canes only when they are dead, severely damaged, unsightly or more than 3 years old. Old canes can be identified by their gross thickness and grayish color. I do prune the ends of canes which have suffered winter kill. Unless I want a bramble effect for wind screen or privacy or to cover an unsightly area, I prune out some or most of new canes as they emerge, retaining only three to five major canes.