Deadheading, or removing dead flowers from plants, prevents flowers from going to seed, which in turn causes them to bloom more profusely the following season. In some cases this will even cause the plant to bloom again in the same season. When deadheading, pinch or cut the dead flower at the bud or the nearest joint.
Cutting back involves cutting the flower stems on perennials that have finished blooming. This is usually done for neatness but can stimulate an additional round of flowers on certain plants.