You can keep nonwoody annuals and perennials flowering by using two simple techniques.
Pinching or nipping off growing tips makes a plant bushier. Use your thumb and forefinger to pinch back annuals that often get leggy, like petunias; do this two or three times during the growing season. Perennials that tend to grow rangy, including asters and phlox, benefit from a single pinching in late spring or early summer.
Deadheading simply means removing faded flowers. Use pruners or sharp shears to clip spent blossoms from flowering plants such as delphiniums, roses, and sweet peas. This keeps plants tidy and encourages more blooms. And it keeps reseeders from setting seed.