In my experience, tips are overated.  If you are willing to pay her fee, she will provide you her full effort.

That said, I love giving providers small gifts!  Nothing fancy, and something she can use or enjoy.  A trip to VS, a bottle of wine or perfume, nothing more than $30.  It adds to the anticipation!!!

Many ladies post a wish/gift list, with at least one reasonably priced item.  Go for that, it shows you actually read her site, not just saw her pictures.

A $20 Starbucks gift card has made a fantastic impression for me on more than one occaision!!!

A gift is something you normally would give to the provider when you first arrive, a tip is usually offered at the end of your session. Lower priced providers, especially agency providers, usually prefer a tip as that is theirs to make up for the lower price and if with an agency they do not have to split it with the agency. Personally I do one or the other, depending on who I am going to see.