Summer flowering shrubs like Spirea, Potentilla, Weigela, Hydrangea and even Roses should be pruned in early spring before growth begins and then again later in season to remove spent flowers and encourage more blooms.
If this all appears a little daunting, give me a call and I can arrange to have a trained professional come by to take care of your pruning needs.
Photo courtesy of http://natureswayinc.com