Thaw the chicken breasts thoroughly in the refrigerator. Place them on a plate because the vacuum pack may leak. Do not use the microwave for defrosting. It will have a tendency to precook the chicken breasts.
Fill a used catsup bottle (or another squirt bottle) with water and have it available to douse any flames that may flare up.
Watch the chicken breasts and observe when they lose their clear appearance. When the chicken breast is completely white on one side it is ready to turn over. Do not constantly turn the chicken breast. It is ideal if you only turn it once.
Be careful not to over cook your chicken breasts. Chicken breasts are thin compared to steaks and are therefore easily over cooked. When the chicken breast is white, it is done. If you want to see if the chicken breasts are cooked cut on the edge of the chicken breast rather than in the middle.
If you are using barbecue sauce, spread it on the chicken breast one minute before you take it off the grill. Cook for thirty seconds on the first side. Then spread the barbecue sauce on the second side and cook thirty more seconds.