I second the fitday suggestion - you can plug everything in, and even use it sort of as a meal planner.
If you're looking for 'rules' then, I'd go with the following:
Get plenty of protein.
Less processed is better than more processed. Apple > apple sauce, etc.
Some meal suggestions:
Hard boiled eggs + fruit. (You can boil eggs right!)
Scrambled eggs with some cheese & veggies.
Greek yogurt (plain) with frozen fruit and maybe some splenda tossed in.
Sammich with high fiber bread & your favorite fixing, and maybe toss in some sprouts or lettuce or other veggies. (I get 'Our Daily Bread' which is in the freezer section - although not available at Wal-Mart)
Oatmeal (I like the Quaker weight control because it adds fiber and tasts good) or steel cut oats.
Baked chicken boobs, maybe with some cheese sprinkled on top.
Frozen tilapia (I get it in bags at costco, toss on some lemon juice (from the plastic lemons), salt & fake butter spray, than microwave for 3-4 minutes) Eat with some veggies and/or fruit.
Tuna fish mixed with avocado & greek yogurt. Serve as sammich, or on greens for a nice salad.
Grilled sirloin with a salad or some veggies/fruit. Make with sweet potatoes. Mmm.
Now, calories still matter. So obviously if you eat 2 lbs of chicken then it's not the same thing. So you'd want to check it. And these aren't the only things you could eat, they're just some relatively simple suggestions of things you could do that would be perfectly fine and shouldn't be too hard to cook. As you get bored you can look into learning to cook more and ask for more recipes. There are a lot out there, and as long as they fit your calorie & nutrient goals you should be golden.