I'm one of those food fitness geeks and this post seems long
I'm someone who for whatever reason finds it fascinating to count calories, pay attention to everything I eat, blah blah. First, a good calorie tracker to just find out how you are doing in general is fitday.com. Go there, sign up (free and easy), and put in what you are eating. At least you can get a good idea of your total caloric intake on your average day. Your meals should be broken into 5-6 a day. Go to
http://www.bodyforlife.com/exercise/tools.asp and use their calculator to get a rough idea of how much protein, carbs, and fat you'll need to build/maintain muscle and lose weight. I think the site's general content is good but make sure to supplement it with other information. The calculators are good though. Anyway, I need around 2160 calories a day to maintain where I am. I'm currently around 15% body fat (I'm lazy in the winter and don't ride mtb or road as much) and down to around 8-10% during the summer. So, I eat a 500 calorie breakfast, a 300 calorie snack, a 400 calorie lunch, another 300 calorie snack, 400 calorie early dinner, and 200 calorie protein shake before bed. Everyone is different and you may want to play with your carb levels depending on how much cardio you do to make sure you're fueled up. I'm in the gym as much as I ride. Currently that's 4-5 mornings in the gym, 2-3 days of mtb, 2-3 days of roadbiking. So, I eat more carbs than I should.
As far as what to eat. Protein: Egg whites, beef (sirloin, roundsteak, extra lean (8% fat) ground beef, ground lean turkey breast, skinless chicken breasts, turkey breast, low fat milk, whey protein powders, cottage cheese, low sugar yogurt. Carbs: Whole wheat anything (check the ingredients and make sure first ingredient is whole wheat/grain), whole grains, etc. Oatmeal is great but watch the sugar quantities in the instant stuff. I do eat regular pasta but try to make the majority of it whole wheat, but it is not as tasty. Avoid white bread, pastries, and basically anything made with "enriched flour" or bleached flour. No nutrient capability whatsoever really. Fats: Olive Oil, grapeseed oil, flaxseed oil, is pretty much what I stick to when cooking. Also get fat from my milk products like cottage cheese and yogurt. Finally, lots and lots of fruits and vegetables. Especially things like romaine and butter lettuce (avoid iceburg), tomatoes, leafy greens, brocolli, couliflower, etc (sorry if I spelled anything wrong).
My partner here at work is a nutrionist for teaching kids and medically at risk people how to eat better and she's helped me quite a bit on what to eat. My wife is a gym rat and rider also and has managed to signifantly change her body and is very lean at this point following this system. I can usually drop a pound a week with no problem if I track my calories and avoid overdoing it on sugar (I used to be an addict so hard change). Remember, don't starve yourself ever and make sure you eat some fun foods also.
If you have any other questions send me a PM and I'll see what I can do. Hope I didn't bore you too much.
SC