They are done when the juices run clear when you cut into one. This recipe is great.. here is my modification:
http://allrecipes.com/Recipe/Easy-Ro...en/Detail.aspx
I use one can of cream of chicken and herb soup and mix it with a splash of milk first to thin it out (2%) before pouring it over the chicken. I also use light sour cream. It makes an amazing gravy and is delicious over egg noodles.