The laws of food combining can vary somewhat depending on the source, but the most common rules include the following:
Only eat fruit on an empty stomach, especially melons.
Don't combine starches and proteins.
Don't combine starches with acidic foods.
Don't combine different types of protein.
Only consume dairy products on an empty stomach, especially milk.
Other rules include that protein should not be mixed with fat, sugar should only be eaten alone, and fruits and vegetables should be eaten separately.