As others have said every guy basically likes something different and some guys have things they really don't like. I think what makes a BJ a good experience is that the lady seem into it and be able to listen to her partner.
For example i really dislike that uses her hands alot during the BJ. Most providers i've been with that use their hands have been cool when i've asked them to not use their hand. It's those times when i'm getting a good BJ and the lady starts using her hands and i say, "could you not use your hands" and they continue that kills it for me and it becomes not enjoyable.