To start, I would say there is nothing that will guarantee a great date, since it takes two people (or more, lol) for that to happen. The guy (or girl) could do everything in their power beforehand, but that doesn’t necessarly mean the date will turn out as planned. Still, a few things can certainly improve the odds:
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The first, and most important, imo, is doing your research on the lady in question and making sure its done well. If there is something a client really wants say, a certain look or a specific sex act, then do your best to make sure thats a near certainty, or at least a strong likelihood, before making the date. Ending up with someone who is essentially incompatible with you is a recipe for disaster, or at the very least, can be deeply disappointing. And thats not the providers fault if you want to do “X” with her but, by all public accounts, she only does “Y.”
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Second, I also make sure I’m early for incall. By that, I mean early to the area, not early in contacting the provider to say I have arrived, lol. Nothing puts me in a worse headspace than getting anywhere late, so depending on distance, I usually try to get to a nearby hotel or coffee shop 30-60 minutes before our scheduled start time to chill out and relax.  
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Third, is keeping expectations in check. Thats somthing I have learned over time, as it wasnt innate. It can be hard for many women to fully recreate the look they present in their photos, which is why I appreciate providers who have a healthy mix of professional and selfie shots. If she looks as great as her pro shots, thats ising on the cake but it is something i dont really expect.  
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Lastly, dont prejudge the situation. You may walk in and the room is a mess, or the provider could be distracted by something that happened just before you arrived or whatever. It’s helpful if both sides can give each other a bit of grace and understanding at the start and let each other settle in a bit.  
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None of the above guarantees anything, but in my experience, it makes it more likely for the date to go spectacularly well.

Your list is all very good... for people with XYZ # of previous encounters.

You've said "finally formulated a coherent answer: I love it when a man is completely, unapologetically clear about what he wants."

That's great, for you, and him.

I've had less than 8 encounters. I have no idea what I'm to expect, or request.  Ever. I look forward to that day.

I just do me and that usually works pretty damn well. No game plan necessary.

Show up clean with a full envelope. Be pleasant, respectful and (if you can) funny. And, yes, don't be shy about telling her what you want.

Hygiene:
- brush your teeth, brush your tongue, and swish for at least 30 seconds with mouthwash, preferably gargling with it also.  
- facial hair: please do not show up with stubble. Either have it long enough to where it bends instead of poking, or shave as close to the appointment as possible.
- Washing: wash behind your ears. Wash your neck. Wash in all of your skin folds, lifting them up and getting in all the way. Wash your ass crack all the way to your butt hole. Think of your pubes like your scalp and basically shampo them and use your fingers to scrub the skin underneath. For the love of God, wash under your foreskin and then dry it well. Wash the back of your balls and your taint - I can’t tell you how many times everything smells fine until I lift the boys up. Wash your feet and in between your toes.
- Underarms: please wear deodorant WITH ANTIPERSPIRANT. Even if you’re normally a hippie who avoids aluminum. It really sucks when you smell good at the beginning of a booking and then you start to sweat and you start to stink.

Listening: WATCH as well as LISTEN. If you’re thinking about touching the pussy, start light and gentle and then look to see whether she looks like shes enjoying it and is feeling teased like she wants more. You can always go harder later, but if you start off too hard and hurt her, you both have to recover from that.
- ask her whether she would like you to go down on her, rather than asking if you can. If you’re genuinely interested in giving pleasure, the first step is to ask whether the pleasure is wanted. If we agree to it because you obviously want to even though we’d rather not, I promise you’re not actually giving us pleasure.

Respect: this has so many dimensions. Don’t try to negotiate her rate. Don’t make her ask for her envelope. Take no for an answer, without pouting.  

Oh, and FEEDBACK: if we look beautiful, tell us. What we’re doing feels good, tell us. If you just had an amazing orgasm, tell us. (If, on the other hand, we’re doing something that isn’t quite working for you, please tell us, so we don’t keep doing it rather than letting us keep struggling, which just wears us out.)

Quick answers: research and respect. Do my research before reaching out. Treating her respectfully throughout.  

As for expressing the exact specifics of what I’m looking for, I struggle a bit here. I’m getting better about requesting some preferences (clothing), but I find it difficult to say what I’m truly looking for without crossing the lines of what we’re allowed to talk about. I’m typically into fairly vanilla stuff (GFE, sense of connection, DATY, etc.). Some ladies I’ve seen give me a clear opportunity (phone call to discuss the session, video chat) to be fully open and honest.  This is very much appreciated. Most don’t provide that window and communication is short and sweet, strictly business. By default, I don’t want to cross the line of what to say, so I simply research and hope for the best.  

Would love to know better how to straddle the line of getting across what I’m looking for ahead of time and keeping each of us legally safe. We both win in the end when the experience is better choreographed.