These are questions you should be asking yourself if you're trying to burn body fat or gain muscle mass. If your answer is counter to what is suggested below, then make adjustments as necessary. Food can be enjoyed but when you have goals, food has utility. Its only purpose becomes to fuel your body. Treat food and exercise with respect.
Has it been more than 2-4 hours since your last meal? If so, then it's time to feed.
Eat a serving of protein with every meal. Women should have 1 serving, men should have 2 servings.
Does your meal have vegetables or leafy greens? You should eat 5-10 cups of vegetables/leafy greens a day. Any way you want.
If fat loss is your goal but you didn't just get home from the gym or seeing your trainer then put down the pasta, bread, tortillas, rice, and other starches. Instead, double your fruit and vegetable intake. If you have just worked out, a mix of healthy carbohydrates is fine.
You need fats in your diet from animal sources, oils, nuts and seeds. Spread fats through your day as you eat your meals.
Adapted from the book Specialist in Fitness Nutrition by John Berardi Ph.D. and Ryan Andrews, MS/MA, RD.