Food combining. This means not eating starch with protein, and eating fruit on an empty stomach.
If you are careful about what you eat, you can pretty much eat anything that some tell you not to. For instance, if you eat it on an empty stomach, you can eat pineapple, or banana, or any fruit that you would usually have a problem with.
Also, you need to eat as naturally as possible - so fruits and veggies are great. Processed foods are really bad.
And don't eat about 3 hours before bed time.