Hi Cheeseheader!
I don't know if this is right or wrong, but I don't break my calories down. I just eat my typical meals and snacks. At the end of the day, I'm usually right where I need to be, but maybe that's because I've been doing this for a while.

If I still have some extra calories left, I'll either just not eat them or if I'm hungry, I'll treat myself to a cup of frozen grapes.
Yes, you're right about the 3500 calories = 1 lbs. Here's how I figured things out, but my math is a bit screwy too, so you might want to see what the others say!

I figured out my RMR (resting metabolic rate) by doing a Google search for a RMR calculator. That tells me how many calories I burn per day while inactive. Then, I eat about that amount. I try to burn at least 3500 calories per week via my workouts. That way, I *should * lose 1-2 lbs. per week. There have been weeks when I lost more than that and there have been weeks when I've lost nothing at all (or even gained a bit!!!). I don't really know how to make my body do what I want it to do right when I want it to do it...does that make sense? There are lots more factors that go into it than just pure calories, but maybe somebody here can figure this stuff out better....I'm curious to see the other responses you get!
