Secrets for soft cookies:
1. As someone said above, baking time. Bake longer, at lower temperature. I use the Mrs. Fields recipe (but I don't like her chips, I use Ghirardelli bitter sweet), which calls for (I think) baking a dozen at 300F for 18-22 minutes.
2. Use parchment paper under cookies. This prevents cookies from scorching and getting runny and flat, and therefore crunchy. (Silicone baking sheet liner thingy probably works even better, but I haven't tried one.) This also prevents them from getting all messy and destroyed when you scrape them off the sheet. They just slide off the paper, and the cookie sheet stays clean. I'm pretty sure this also eliminates the need for a really good airbake cookie sheet (they have a layer of air in between the metal).
3. Refrigerate dough before baking (like, at least 1/2 hour and then in between batches). This prevents them from spreading too quickly and getting runny, flat, and crispy/scorched.
4. As someone else mentioned, I think using more brown than white sugar has something to do with it too, since the Mrs. Fields recipe follows that pattern. I prefer dark brown sugar because it's moister and makes the cookies darker and yummier.
5. I also beat the egg (lightly!) with the vanilla before adding it to the other stuff (general baking rule not to overmix eggs); am careful to shake the flour into the mix rather than dumping it (keeps it fluffy, introduces air), and make sure butter is softened (should be able to press your thumb into it) but not liquidy (or cookies will be like cheap leather). To clarify about the flour, rather than dipping the scoop into the flour, I use a spoon to shake the flour into the measuring cup until it is slightly overful, then scrape (don't tamp!) the excess off with a knife or something with a flat edge.
Here's the recipe I use:http://www.copykat.com/component/option,com_rapidrecipe/Itemid,28/page,viewrecipe/recipe_id,342/
Since using this recipe and these methods, I have gone from making yucky cookies to awesome ones. It might sound like a lot of work, but it's only a little more than just doing it the way most recipes call for, and it is totally worth it for awesome cookies.
Follow these rules, and your cookies should be chewy (but not in that nasty squishy way of soft supermarket cookies), almost perfectly round, and of even thickness rather than flat at the edges. Most of these rules probably apply to other types of cookies, but I just happen to make chocolate chip cookies all the time.