After the blooms fade, prune 2 to 3 inches off the branch tips that flowered. If you want to prune the shrub to make it shorter, cut 1/3 of the oldest branches back 12 inches and prune the remaining stems creatively to produce a beautiful layered look.
Watch Mark's video tip on pruning Azaleas.
Carefully remove the dead blossoms without damaging the small leaf buds that have formed just behind them. If your Rhododendrons have gotten too tall, use the pruning method mentioned above with the Azaleas to bring them back down to size.
Prune Forsythia right after the blooms fade to shape them up, thin them, and remove old wood. Take the oldest branches right back to the ground - do not leave a stump or undesirable new growth will develop.
Watch Mark's video tip on pruning Forsythia.