If you just beginning your garden and have an empty site to work with, you should really consider trees, shrubs and vines first. These plants will provide the overall structure for your garden and you can fill in with perennials, annuals or roses later. If you already have some trees on your property, try and visualize how you can integrate them into your plan.
Trees also provide an invaluable service as they provide much needed shade.
By the time June rolls around and the heat and humidity set in, you will be thankful for them. Trees are best planted while they are dormant. I have found that January and February are the best times to plant trees. There are numerous vines that can be grown in the South and they can become addictive. Vines can be used to cover arbors, trellises, or fences.