I always plant a lot of white flowers, including fillers like baby's breath and statice. White blends perfectly with other colors, brightening dark arrangements and softening intensely colorful ones. Another consideration is the shape and size of your blooms. Here again, a mixture is best. It should include eye-catchers like tall spikes, daisylike blooms and dainty fillers.
Some plants have marvelous leaves that look great in arrangements.
Coleus and amaranthus come to mind. The ideal cut flower has a tall, stiff stem, a lovely fragrance and lasts at least a week after being cut. Oriental lilies, peonies, asters, Shasta daisy and hydrangeas come to mind. This is what florists insist upon because the time between cutting and selling can be several days, with a lot of handling in-between. This is where home gardeners have an advantage over florists.