It would be helpful to know the species, as the timing and method of pruning differs with each. Generally speaking, with flowering shrubs you would prune immediately after flowering was completed. Some shrubs, however, bloom on so-called "new wood," so they can be pruned in late winter or early spring, before new growth begins. I really can't give you specifics without knowing the species, but for more general information on pruning, type in "pruning" in the bhg.com/gardening search function.
Luke Miller, editor
Garden Ideas & Outdoor Living magazine