My approach is very straight. If the person vibes well with me and I am comfortable, only then we decide to go ahead with the shoot. But, if a person makes me uncomfortable or throws attitude at me, I would not like to work with that person. However, till date that hasn't happened to me.
I am not a pushy person at all. I let the star wear whatever he or she wants to wear. I don't force my opinion on anyone.
In fact, a lot of photographers have an attitude. More than the stars themselves. But I have had no problems with anyone so far.