First thing's first: get your shots! (I know you already mentioned it, but this applies to anyone just now reading this.)
Second, utilize common sense that you'd use in your own country. Wash your hands after using public restrooms or handling anything that might be "dirty". Keep a little bottle of hand sanitizer on you at all times. Try not to get yourself caught touching door handles (use your feet to pry doors open, if you can).
Third, read up! There will be foods and other intricacies in India that your body will not be accustomed to that might make you sick. Read up on the foods you'll be consuming, and keep a list of the foods you should avoid due to allergies and the like.
Fourth, keep medicine on you during your travels. Aspirin, cough medicine, and anything else that could benefit you from viruses and nasty illnesses.
Hope this helps!