It depends upon what kinds of shrubs you have. As a rule of thumb, we prune spring flower shrubs right after they bloom. These are shrubs that bloom with or before purple lilac. Remove the unproductive wood and spent flower clusters to make room for new growth. At the end of the season this growth will form flower buds that will open next year.
Summer flowering shrubs usually flower on current season's wood.
They are pruned during the dormant season, and considering our warm spring this is about over this year. Next year, prune these in March or early April, after danger of severe frost has passed by before the buds begin to swell. Most trees are also pruned during the dormant season in early spring. Bleeding does no permanent harm to the tree but is messy and a nuisance. Be sure to use NO tree wound dressing on those cuts.