i heard somewhere that u can't really fake crying, u just gotta really get into your character's shoes, maybe connecting it to a similar (yet more trivial) moment in your life. this is dangerous tho cause imagine playing 100 performances and thinking about your dead parents on cue every night! but if you think about your dead childhood pet, suddenly the emotion is there, minus the psychological damage.
but yea, crying onstage will only work if u find some sort of button for yourself during rehearsal, some way of looking at what is happening in the show, that will work every time.
personally i went to see little shop twice during the summer, and the girl that was audrey didnt cry the first time and cried the second, but the first was just as sad and believable so no damage done.
in other words, real tears are cool if you can get them and then control them (u dont wanna sob incontrolably during a song or line either), but regular "dry" acting works just as well.
Tenme por lo que soy, por lo que puedo ser, y si te importo hoy, tenme nena, o vete!