How much to tip a Massage Therapist?

I am seeing my massage therapist soon. If she does much more than a very good job on me how much extra should I tip her. Her fees are $ 50 for 30 minutes for full body massage.
I do not want to emberrass myself by giving her too little money.

The customary is $5. But, of course, if you really like your massage therapist you will tip her more. Im a massage therapist and have gotten tips ranging from $5 through $20. It all depends on how good you think your massage experience was.

Is it her place? or does she rent a room at a room sort of situtation? - eh, as a general rule of thumb, I would say 5 if its decent, 10 if its really good. If it is spectacular, give her ten bucks ask for a card - and let her know you will pass it on - then do....