Journalling my food works for me. When I say "works" I really mean, keeps me on track. If I'm actually inputting it into fitday, I have think about it and add it up. Thinking about the calories can be a slap in the face. I can lollygag around and think I'm being straight with myself but it's hard to do (for me) if I'm not writing it down.
Just a few moments ago, I input my breakfast and my lunch, and my activities, into fitday. I don't remember when I last did that but I know I'll be updating it later today (for dinner) and again tomorrow. I need to do it and I will.