i tend to the major pruning in the spring
- early/mid march before new growth starts. i do a less intensive prune in the fall - just to get the tallest stuff off in case of bad snow as i don't want any damage done. others do their main pruning in the fall.
you can cut the bushes back to about 2 feet tall. or leave them a little taller if you'd like. if you have a branching that you like, trim back to just above where the branching starts...if you go below, you might not get the same growth pattern next year.
also, take a look at the canes to see if you see and nodes - if there are nodes on the inside of the cane, cut below or the new growth will be inward rather than outward.