Wear white, not bright colors. Try keeping a few clippings of mint on your table, or tied to your waistband.
A spray bottle of water can be used to soak them, and step on them.
Put a little wad of newspaper or something in a brown paper bag, tie shut, and hang upside down. Wasps are territorial, and will probably avoid anothers nest, even though it's fake. I'd crumple the bag a little before stuffing. They also sell fake nests, but I don't know how much they are.
http://eartheasy.com/live_natwasp_control.htm