Dieting is easy.
Food consumption -> Calories In
Exercise -> Calories out
Maintain a deficit of calories to lose weight.
3500 Calories = 1 lb body fat.
Exercise is good to keep you from losing too much muscle mass as well as fat.
Nick's got everything you need to know right there. I've lost over 20 pounds in a bit under two months from just doing the math. At my age, size, and activity level, my maintenance caloric intake is 2500-2700. If I wanted to lose a pound a week, I'd cut that 3500 he mentioned, and lower my daily intake to 2100. I wanted to lose the weight faster than that, so I've been eating right around 1900 calories a day.
You don't mention how many meals a day you have, but I'd watch out if you're really down to only 1500 calories. For a guy your size that could easily put your body into starvation mode, and after a good week or two you're not going to be losing anything.
Me, I find it easier to have smaller meals more frequently throughout the day. I usually have a low or nonfat yogurt for breakfast, a banana or fruit cup for a morning snack, a wrap and veggies or crackers for lunch, a lean cuisine for an afternoon snack, a small dinner, and then two beers or a healthy rum and diet coke for an evening snack. If I know I'm going to splurge on one of those meals, I'll cut out some of the snacks. Other than booze I only drink water or diet sodas. (Also, if you're going to drink, generally clear liquors are best, followed by Michelobe Ultra. It tastes bad, but its stats are great and it's 4.5% ABV. Most light beers are closer to 3.)
And, as you can tell from the frozen meals, the booze, and the diet sodas, I'm not really a healthy eater. They key to me has been making it easy on my daily routine. Each morning I spend five minutes in my kitchen throwing stuff in a bag so I'll be able to eat all day at work whenever I feel hungry. And since I bring my food with me, I'm not tempted to run out for fast food or hit the vending machines.
It's amazing how much more filling a wrap on a low carb tortilla with 3.5 (small) slices of turkey, one slice of cheese, lettuce, tomato, onion and mustard is compared to a small bag of chips. And yet the ones I make are only 190 calories.
But, since you asked for foods you can munch on without feeling guilty, the best are air popped popcorn (no butter), and pickles. For everything else, try eating half servings--you'll get used to them pretty quick.