Healthy alternatives when eating fast food?

So lately I've been thinking about trying to be as healthy as possible over the summer. While I don't always eat out or at fast food places, I know that every once and a while, or when I'm with friends getting lunch, I'll probably go somewhere like that. I was just wondering about some healthier alternatives at common fast food places... like Starbucks or Taco Bell or something. I always lean towards Subway because I have this certain sandwich that I make, which has a good amount of calories, hits all of the food groups, and doesn't have too much bad stuff. I mean, its probably not the healthiest thing in the world, but its better than a double double extra large cheeseburger with a giant milkshake! Anyway, some alternatives would be nice for when I'm in those situations. Thanks! :)