There are alot of tricks but good lighting is key and natural lighting is the best.
Here are just a few tricks:
Blowtorch, for browning the edges of raw hamburger patties
Motor oil, as a stand-in for unphotogenic syrups
Cotton balls, which, when soaked and microwaved, create the illusion of steaming-hot foods
Spray deodorant, which gives grapes that desirable frosty veneer
Brown shoe polish, so raw meat appears to be just-out-of-the-roaster succulent