Find a pot or vase that fits your purpose. If the arrangement will be a centerpiece, choose a container that won't dominate the table. If you intend to hang the arrangement, choose a hanging container. Also, consider a decorative pot or vase over a plain growing pot.
Place plenty of greenery, which helps colored flowers stand out, in the container. Use a variety of greenery to enhance the look.
Arrange the flowers around and into the greenery. Make some flowers dominate the greenery by standing above or on top of the green. Allow others to sink back behind the greenery to produce a hidden look that requires viewers to move closer to the arrangement.
Use dirt if at all possible. The dirt will keep the plants in place and provide the realistic qualities of sight and smell.