Wezt, I try to maintain some kind of communication with my provider, really helps if SHE has a bit of a personality; that can accelerate my interaction, which can lead to touching, pointing, and other forms of communication because many of the providers do not speak much English.
I have worked with a variety of providers over the years; but, this is my first full year of dealing solely with
AMPs and I have NEVER had to tip first, yet. However, I have heard of some who ask for tips up front; if they do, that makes things really easy: negotiate or leave. Right? I have had one ask in a hinting fashion, using such words as "You take good care of me?". Treat them fairly and respecfully and you should do well. If they are dissatisfied with what you leave, I am sure they will find a way to tell you so. :-)