I would either plant hour glassed shaped plots or "L" shaped plots and definately keep them less then an acre of you plan to hunt ove ther them. I've attached a great link to an article in the whitetail news about food plots, hunting food plots and food plot design. It goes into detail about planning and creating plots. it's a good read and quite informative
http://www.whitetailinstitute.com/in.../aug03/11.html