On an incall date, is it expected that the Client bring the drink of his/her/their choice? Or is it expected that provider have something on hand to help entertain?  What I drink is fairly expensive and specific I generally bring my own, but I am just curious.  Also on another note, what is the best way to communicate special requests discreetly? I was told recently by a provider that if I wanted Greek I should have let her know in advance, but how does one do that without risk to yourself or the provider?

While many providers do offer some libations at their incalls (usually water, juices, or occasionally wine.), not all do.  If you need to have a specific drink to get you in the proper state of mine, then yes, do bring your own.  Don't expect the gal to have a bottle of Louis XIII cognac on hand.

As for how to tip off the gal that you want to visit Greece:  That can be tricky.  Discussion of sexual activities is often a sure  path to being cut off, so stealth is required.  If the gal offers two price options (without and with greek), then I think it is fine to say that you are opting for the premium session.  She should catch on from that.

The problem is with gals who perhaps make no mention of greek, but reviews clearly reveal that she offers same.  Here you could make mention of the reviewers who did mention greek, and say something like you read their reviews and want to have a similar session.  I think this is innocuous enough to not offend, while transmitting the message as clearly as possible.

Then there is the use of code words like "greek isles, back door, etc., but that could cross a line with some gals so be wary of it.

and I very often have wine.  But given that your choice is specific and expensive, I think you're better off bringing your own, at least until you establish a good enough relationship with someone who knows what you like and is willing to provide it.  

Refreshments are provided by some. I always provide a choice of water, soda etc if incall but above that depends on length of time. If an hour is planned a cold drink is appropriate in my eyes, if a longer stay common for me to have fruit, cheese and sometimes wine. Not trying to discriminate with time but usually within an hour meeting no time for the nibbles. If you have a favorite liquor probably best that you bring. Better to have on hand then be disappointed. Wine, liquor etc varies with time of day as well. As far as specialty performance questions.....as Mr fisher stated tough call. Better to complete screening first, I know that sounds ridiculous but your lady won't be comfortable with any specific talk or codes until she screens you. After screening I will ask for attire requests etc, if gent passed screening and I am planning on private time then ok to talk a bit. Perhaps you could reference specific review that mentions what you would like. " read and loved your review by so and so......hoping for same wonderful afternoon with you". She will then know which review to reference and no inappropriate lingo!

...shouldn't mention it before the first time you see a provider.  It may turn out you're "overqualified" anyway.

BYOB is fine. You ask a VERY good question about Greek. Once I am verified, I carefully ask about specifics. This can be a little uncomfortable, but the provider may need to be prepared before she allows it, so she may want to know ahead of time as well.
My issues have been regarding CIM. Some providers have reviews that say no and others that say yes. I like to know if it's going to be an option ahead of time. A carefully worded question usually gets a response that may not be a "yes" or "no" but leads me to know what's on the menu.

soft drinks are fine.  One should not presume on alcohol...  some ladies & gents are on the wagon or choose not to.  Anything which is brought should be in sealed containers, opened in front of her or by her.  
I would not know how to approach the Greek Isles on a first meeting.  My thoughts are she'd like to look at the goods before committing.

I find that most of us definitely have bottled water available as well as other soft drinks (sparkling water, soda, flavored water etc). I also have a variety of wines available just in case the occasion calls for it (Sauvignon Blanc as a white, Rose and of course a Malbec). If your beverage of choice is rare and expensive is a good idea to bring it with you, but of course let the lady know that you are bringing it as some providers do not drink. If you plan on sharing it with her, make sure is sealed and new e.g champagne. Regarding requests, I think that once you get  screening out of the way and you are good to go, you can politely ask her for that particular service being that it takes some hygiene measures. Also if you have clothing requests in mind, I totally recommend that you let her know in advance so she can either look for it or purchase it, some of us have tons of outfits but some requests are hard to fulfill when advanced notice is not provided.

Providers tend to be more selective about it...As you mentioned, how you approach is ideal in order to get a very straight forward answer, but wait until you are fully verified, otherwise it is a red flag for us.

When I get a P411 request or email for a date, I always read the clients' profile.  There I can see what he likes to drink, although I might not have it I will know if he is a drinker or not. Most guys put water/soda or red wine/liquor. Another thing is I get to see what is important to them such as dfk and Greek; that way I can also decide if we are a good match and have an idea what he may like or be expecting.