Hi there; welcome! Here are my thoughts on your question.
Eat enough so you don't feel like you're starving. Use FitDay to calculate how many calories you burn per day, then figure out what is about 500-1000 calories per day below that (for a loss of one to two pounds per week), and eat that many calories. A general rule of thumb is not to go below 1200.
Also, be sure not to skip meals; don't go more than 4 hours without eating. Many people do well having 6 smaller meals as opposed to 3 main ones; others have regular meals but small snacks in between. Protein and healthy fats keep you fuller than carbs, so make sure you're eating them and not just jumping on the fat-free bandwagon. Finally, be sure to get your fiber...that also keeps you feeling full.
Feel free to join in the forums...lots of tips and laughs there!
"If you drop an egg, you don't say, 'Oh, shoot' and drop the other 11, do you?"
-Source unknown, but obviously brilliant
Reached goal 4/16/2010...but kind of afraid to look these days