Most chain restaurants have nutritional information available on their website. Download this info in advance and figure out one or more healthy meals and write these down (including any modifications such as omitting mayonnaise on a sandwich) and carry this list with you.

That way when you decide to go to that restaurant, instead of being tempted by what's on the menu, you'll already know what is safe to order. This is much easier than trying to do calorie calculations after you're there or trying to guess what meals are actually healthy (you might be wrong).

I usually figure out a few different meals in advance to fit different moods, such as a healthy salad if I'm not especially hungry, a lean sandwich with fruit for a lunch, or perhaps a grilled chicken or fish with steamed vegetables for an evening meal. You can make these kinds of decisions on the spot, but it's a lot smarter to do in advance when you've got all the nutrition info in front of you and you aren't starving.

I usually stay away from desserts at restaurants -- most are not healthy and have hideous amounts of calories. Instead, I wait until I'm back home where I can fix my own healthy low calorie dessert. If you're really needing a dessert and can't go home, a bite or two of a friend's dessert usually is okay (or package the leftover and take it home if you're by yourself). But be sure you actually do limit it to a bite or two. That's hard to do, so I keep a few 100 calorie chocolate chip granola bars in my car just in case I need some carbs or have a serious sweet craving.