Parenting 101: How to get your kid to eat

Some of you may know that Jacob is a VERY picky eater. He goes through phases of food. There was the pancake and bacon phase, then there was the peanut butter and potato chip sandwich phase, then the corn dog phase. Now Jacob won't eat ANYTHING! He just refuses to eat. So when he came up to me yesterday and asked for cheese and cookies I didn't hesitate to give it to him. He won't eat my pot roast and potatoes, but he'll eat a thin mint cookie and cheese...I don't know what to do with him!