The classic catering trick is, of course, to put boxes under some pretty fabric.
Photo by Upper Crust Catering. Look how much more lavish and interesting that looks than if all the platters were on a flat table? It's also an easy way to incorporate beautiful fabrics in smaller quantities than it would take to make an entire tablecloth.
But my very favorite way to create elevation is with cake stands. They're available in an astounding array of designs, from elegant to whimsical to rustic. You can even make your own, like I did for the Cornish Fairy party I designed:
Or for a gorgeous eclectic look, you can't beat these designs from Crafty Clementine on Etsy and Wedzu: