It is a common thing, and no provider imagines their clients are experienced or even good. The provider really won't have any animosity towards it but it is something you could bring up if you want to. Honestly the advice I would give you is to make your first time great. Do your research on a girls for a while, read all their reviews, check the reviews of the reviewers and make a small list of girls in your budget. Try to spend a decent amount, obviously what you can afford and get a great girl and I would suggest for a longer than 1 hour encounter. The biggest hurdle you will face is getting to see the top girls as a newbie. There are a few who have alternative screening methods that aren't invasive into your personal life and those would be ideal to you but some might ask to meet for a drink (time you pay for) to get to know you quick and make sure you're safe. Others are giving some personal information out which I wouldn't suggest to a provider. If this is something you plan on continuing, I would honestly invest in p411 and allow them some personal information to verify you. They are extremely trust worthy and delete the information after you give it to them.

I can't speak for all providers, but most like to have references from other providers that you have seen.  If your new "for the most part" I'm assuming you wouldn't have any references and would say so. Being new isn't a problem. If you let the provider know, she may be able to answer any questions you have Good luck and welcome!

Q: Do providers assume their clients are experienced?  
My A: I don't know for sure, but I doubt providers necessarily assume every client is experienced.  I suspect they can quickly read clients to figure out if they're experienced or not.  They can probably figure that out in the screening/booking process as well as your first few minutes in the room.  One thing I'm pretty sure of is that your skill level is not really that big of a deal to most of them.  You're paying them, not the other way around.  They are the service provider; you are the client.  They're more focused on making sure they do a good job and fulfill your fantasy, not so much on how well you're doing for them.

Q: Is this something to discuss with a provider or just go with it?  
My A: Your call.  Not sure it will be a big deal one way or the other.  If it were me, I'd probably just go with it.  At most, if I got a funny look in the session like "WTF are you doing?", I might sheepishly admit that I'm a bit inexperienced in the hopes that it comes off as cute and charming so she'll cut me some slack.  

If you go with an experienced, well-reviewed provider, you'll be in good hands.  She will have seen just about everything and know how to handle it with skill and grace.  She will be a pro, after all.

Good luck!!

first time. What does "for the most part" mean in your context?

...talking about the before and after of having sex for the first time:

http://www.theeroticreview.com/discussion_boards/viewmsg.asp?MessageID=137638&boardID=33&page=#137638

I had a lot to learn about sex and the hobby.

Probably they either won't be able to tell, or they'll guess and won't bring it up. I doubt you'll have anyone say, "You've never done this before, have you?" They'll pick up on your anxiety, shyness, etc., though, and that they will talk to you about. There's no reason to come out and tell them, unless you think it will encourage them to try harder to make it special. I don't know if that's something providers do.

You're more concerned about how you'll perform, whether you'll know what you're doing, whether you'll make a mistake, and so forth, than the provider ever will be. Which us understandable, but I wouldn't worry. You're going to be with a professional. Let your money buy off some of your anxiety. If it was with a girl you cared about, that'd be one thing. But this way, you can always try again. Practice makes perfect.