Before you get started, think about whether or not you want a theme for your tablescape. Halloween inspires a tablescape with lively and fun elements like decorated pumpkins, plastic spiders and other spooky props. Thanksgiving is another great fall theme, but you don't have to go old school with the cornucopia and horn of plenty centerpieces.
Instead, you can use fall leaves, colorful gourds and all of the wonderful autumn produce. Even if you don't choose an obvious theme, your tablescape should tell a story. You want your audience to appreciate individual elements, as well as the whole picture, but you don't want individual elements competing against others. The overall setting should flow from one end of the table to the other, creating a harmonious vignette.