There is a method. First thing to do is ask yourself "Does this affect the safety of the aircraft & passengers?". If it does then you don't do it (or go along with it) e.g. the captain turns up drunk, well you give him the chance to report himself unfit for duty and if he doesn't do it then you report him unfit. Either way you walk out of that cockpit & refuse to fly with him. Just remember, ask yourself what the implications to safety are.