I've always eaten reasonably well (comes from having grown up on a subsistence farm), so I have never radically changed my own diet, but I have a few (untested)

I've always eaten reasonably well (comes from having grown up on a subsistence farm), so I have never radically changed my own diet, but I have a few (untested) thoughts: 1. Get some food culture. It is easier to make good decisions when they are made in a larger context than "nachos bad vs. carrots good". Learn something about: where food comes from, diet and health (particularly in America: I'm assuming you're American), traditional food cultures, basics of cooking. For me this has meant reading the likes of Fast Food Nation and Michael Pollan, learning to cook some French, Italian and Asian dishes, lots of cookbooks, Alice Waters, Julia Child and other chefs, reading about diet/health studies like The China Study and the Nurses' Health Study, getting myself out to the local farmer's market, but those are by no means the only options. 2. Practice what I like to call "meta-discipline". It is hard to control yourself when you're at home with some junk food. It is easy to control yourself when you're shopping at the grocery store. So don't buy junk and don't have it at home. Before you go shopping, be thoughtful about what you want to buy/eat, make a shopping list, and stick to it. (Usually I think of this in the context of work: it is easy to goof off at home. It is easy to walk to the library. It is hard not to work when you're at the library with a stack of math books.) 3. The biggest improvement to my diet has come from cooking more. Mostly, this happened because I moved from a big city with a bunch of awesome restaurants to a little town with no good ones. I wish I had enacted the change sooner. Good luck.