I like to book massages, mostly via Rentmasseur, mainly because I really enjoy a good massage - therapeutic or otherwise. If it is my first or even the second time meeting a new masseur, I go in without expectations and let the masseur take the initiative. If he does take an initiative, I encourage it put don't push anything. By letting the guy work his magic, it often goes well above and beyond what my expectations are.
My 3 regulars in NYC have known me for a few years in some cases. We have a good understanding of how far the session will go <grin>
In all cases, I tip well.