I transitioned pretty much in one day.  I'm not sure if I'm doing it perfectly, but it's gone quite well so far.  I got some background on it from this article in the NYT:<p><a href="http://www.nytimes.com/2009/10/11/magazine/11Calories-t.html?pagewanted=print" rel="nofollow">http://www.nytimes.com/2009/10/11/magazine/11Calories-t.html...</a><p>and the details from a vigorous Googling.  I'm 6 feet tall, 165 lbs, and probably moderately physically active, so I picked a daily target of 1800 calories.  That was based on some online calculators I found and anecdotes from people doing caloric restriction.<p>You can eat anything.  The trick is not using up your whole quota on empty calories.  If I have a can of soda and a cup of Ben and Jerry's, that's 37% of the day's calories right there, with pretty much no nutritional value.  So you can have junk food, but not so much that it's going to make it hard to get all the nutrients to need while staying under your whole quota.<p>Another guideline is that if you end every day hungry, you're doing it wrong.  Cheese will fill up your quota without filling you up.  Fruits and vegetables, on the other hand, are filling and nutritious without packing a lot of calories.  I shoot for a roughly even three-way split between calories from fat, protein, and carbs.  I don't really use "special" caloric restriction recipes; I just cook/prepare whatever I want, while staying within the rules.  I eat out a few times a week too.<p>Typical breakfast is eggs, maybe with mushrooms or something thrown in, and a fruit.  A lunch might be chicken or fish with salad, or maybe a sandwich (bread is calorically dense, though, so careful).  Dinner is pretty much the same as lunch, except that it's almost never a sandwich, is probably a bit more food, and includes red meat more frequently.  Lentils and beans are all-around excellent, by the way.<p>I do count calories, because it would be too easy to lose track or cheat otherwise.  I use Daily Burn, which has a huge number of foods in their database, and if I eat something they don't have, I guesstimate using things they do have.  Counting calories makes it a lot easier to stick with it, because the more aware you are of what you're eating, the less tempted you are to be naughty.