I've never taken pictures of food, but I have styled food for many, many cookbooks.
Make sure the plates are squeeky clean. Moisten a paper towel with a little white vinegar to clean the plate.
Vegetables looks better when they are not cooked for a long time. For example if you were to shoot a soup, you should quickly blanch the vegetables and put them into broth... it won't taste as good, but will look better.
If you have meat, lightly touch up the meat by lightly brushing vegetable oil over the chicken or meat to make it look juicy.
When shopping, look for really, ridiculously perfect vegetables if you will use them raw or as props.
By the way, you may be working with a chef for this restaurant project, but I would say most food photography ( and certainly all for cookbooks and magazines) are not done with chef's they are done with food stylists. Many times, chefs are the WORST people to style food for photography or video because they don't understand that in order to look good for the camera, the food needs to be prepared or styled differently than if they were to serve it.
