...is ask, and pay attention to the answer! Be open to hearing whatever your partner says without judgment, whether it's a spouse, lover, provider, or client. Listening to someone doesn't mean agreeing to actually do particular acts. But it can lead to more authentic connection. While the element of performance vs. reality varies, with providers I think it's very helpful to have conversations about what you want in a session. If you want a GFE fantasy where the provider is magically into everything that you're into when you're into it (within her limits), say so. If you want a provider to actually share what she might enjoy with you in the moment, ask if she'd be willing to do that.
Besides a conversation, nonverbal cues, flirting styles, talking dirty, what kind of porn someone likes, etc. are all hints as to what revs their engine. To get a hint about providers' desires beforehand, read their websites or social media accounts. If a provider's site is full of photos of herself in black tie attire sprawled across supercars, she might get off on being gifted & modeling upscale lingerie. Often ladies have a gifts section or wishlist that will give you hints as to what they might enjoy. Personally, I advertise "fetish friendly companionship" because BDSM is one of my passions. Providing is a service so I follow your reasoning that sub providers might get off on it more--if they are service-oriented submissives. However from my perspective as a (mostly) sensual FemDom provider, I find it super hot to have men pay me for playing a role that I love, and take control of them for an hour or an evening. Money is a form of power, after all, and I kink on power exchange. One special friend, in particular, has asked to bring My *actual* kinky fantasies to life, and offered himself as a vessel to do that - and it's been exhilarating! During our last session, I hired a hot bi stud for a threesome. Having the sexy male escort fuck me over My submissive friend's bound body as he lapped at my clit is a kinky memory that I'll cherish til the end of my days. A skilled provider could be making it all up because she needs money for her car payments, just like a good somalier could be sick of wine and just putting in time on the job to support a family. But I think many providers tend to combine talent and a genuine enjoyment of their art.I've recently been seeing a sub provider. I'm not that into the Dom part but do find it stimulating to provide directions and thinking of the session beforehand is a turn on but I'm not sure of the motivation of the sub partner. What is it that excites her and is the direction and anticipation also a turn on for her? Not sure how far to push things and it's not in my nature to want to humiliate or hurt anyone. Looking for some advice or suggestions to better the experience for both of us.
"What is it that excites her and is the direction and anticipation also a turn on for her?"
How do we know? Ask her! Some subs are sexually submissive only, and aren't really interested in having a Top tell them what to wear and how to act, unless those things are directly related to the sex acts that are to follow 
Some submissives are more service oriented and love to be told how to dress, how to act, what to prepare, etc. in order to satisfy their desire to serve you in some way. Some submissives are all about taking whatever their Top dishes out, be it spanking, bondage, etc.
The only way to know what excites her is to ask her! When I bottom for someone, it is usually because they want to do something that trips my submissive trigger, and I am quite comfortable talking with a prospective Top about what I like...there are things I have no interest in bottoming for, and some things I won't bottom for for safety's sake, but the only way to find that out about your girl is to ask her!
And, if you're lucky, you won't hear "I want to do whatever pleases you" LOL !!
K
Thank you Mistresskiley.
I swing dominant and submissive...it is a mood and desire thing. For me, the only way to truly understand myself as a human being along with the sexual me is to experience both tops and bottoms. After all we are one organism with complicated twists and turns but we all had a head and a tail. Agreed with previous statements, the most sensual organ we command is the one the sits squarely within the skull. Talk with your provider if you are in the Dom role and see where she will go...but remember this is a relationship that builds over time. I would assume to really experience this with one provider it will take time...time like months of sessions. The trust has to be built...as for the ladies who just tell you you can do 1, 2, 3...but not 6,7,8, well, this is too script to really fell the sensual texture a a true BDSM experience. Certainly open to ongoing convo here or in my inbox if this is a curiosity you would like to explore further. Happy hunting, luv!