Just act like you belong there, and know where you are going, and you should not have any problems.  It's a big help if the provider lets you know ahead of time where the elevators are, saves you looking around.

When you get to room, do not knock like you are trying to beat down the door.

Swim

Do not be talking to her on your cell phone as you walk across the lobby.  If you do have to call her, do it from outside or some place away from people.

Don't carry a big bouquet of flowers.

Do carry an overnight bag like you are checking in.

If you must wait for her in the lobby, get a newspaper and look busy reading it.

so that you don't have to knock.

I think this is a good idea, and I do it when I get the room.

Nothing gives away your plan like knocking.

I bring a gift of candles from Wal Mart in a WM bag.  That helps make it look like I just went out and bought something I forgot.  Every little bit to disguise your true reason for being there helps.

Swim

Are there any standard operating procedures for visiting providers on an in-call basis at a hotel.  I'm imaging one checks out the parking lot, walks straight through the lobby to the elevator, says nothing until inside the room, and keeps an eye out for exits through the stairs.  Anything else?

Yes, ACT NORMAL. Like you would if you were travelling. Carry a newspaper or a book if you want. Just don't look spastic AND AGAIN don't pound down the door!

Summer

Hotel staffs are usually passive, they work in the hospitality industry, and customer service is their number one priority. They should never stop any one from entering the hotel. If they do, get the hell out of there, its a LE. The staff are passive, and will not stop any1 for any reason. Anyways, I never had any1 stop me from going in and doing the deed. I even ask several staff members the direction of the bathroom, bar, elevator on several occasions, and some change for the snack machine. They are clueless as to why I am there. They have no idea, I could be visiting family, friends, business partners, or whoever. I have even been in 5 stars hotels late at night sitting in the lobby, and just walking around outside, talking on my cell phone, talked while I enter and leave, and never been stoped for anything. Heck, I even bought a grocery bag, sandwiches, drinks, or what have you to the hotel. Those staff are clueless as to who enter the hotel.

But don't draw too much attention to yourself though, I may be different because the way I physically look. Don't be too loud, and pretend like you know what your doing. Gently knock on the door. Most of the times, the staffs are busy looking at the computer screens or doing something else like helping someone check in. It ain't too complicated, just make sure you don't look nervous or sweating Anyways, enjoy man.

Nail, meet hammer.

Think back to all the times you've been at a hotel for a "legit" reason... traveling, conference, reception, bar mitzvah, etc.  Has Amy staff ever interrogated you as you what you were doing and who you were seeing?  

This is the easy part.

Interrogated? Definitely not. All of my legit stays at hotels, I was the one asking for assistance. I never got approached asking who am I, what I am doing here, who I am seeing, and so on. That would be ridiculous. If that would be the case, I would simply say, "Excuse me, you have no business asking that type of question", and request to speak to their manager. I hope I was able to answer your question, if I am missing any passive messages, then please inform me.