Restaurants may be able to make healthier versions of their dishes, and there's nothing wrong with asking. Most restaurants just want to make customers happy. Ask if you can get your food baked, roasted or steamed instead of fried. Ask for fat-free milk rather than whole milk. Ask for salad dressing on the side. Part of eating healthy is making minor decisions like these, and you may not even notice the difference in taste.
Although buffets may give you the most food for the least amount of money, it can be pretty dangerous to have "all you can eat." If you're eating at a buffet, challenge yourself. Fill up one healthy-sized plate with everything you want and don't go up for seconds. It takes about 20 minutes for your brain to tell your body that you're full, so take your time digesting your food before assuming that you need more. When you're at a nonbuffet restaurant, stick to one entrée and skip the appetizers and bread. By the end of the meal, you should still be satisfied and will have consumed fewer calories-and will have spent less money.