I find chicken breasts pretty challenging. Not a very flavorful piece of meat, and there really is just a small window within which you can pull them off the grill "done" but not dry.
The first step is to hammer the ckicken breasts out until they are of uniform thickness. I just cover them with plastic wrap and use a household hammer. This will help you in getting an even cook throughout the piece of meat, especially since the window of "doneness" is so small.
The second step is a good marinade. Simple but good is what you see above - first a dry rub of Dizzy Dust , followed by a bath in Italian salad dressing. The longer the marinating time the better - preferably overnight, if you have that much foresight, which I typically do not.
