I was visiting a provider a year or so ago and at the end of a great session I sat on this leather ottoman in the living room to put on my shoes. The ottoman wasn't really stable and it tipped over and I tumbled onto the floor.

Pain-free parking is a must. Preferably street parking nearby or if a hotel, one that takes cash at the exit.  
On the subject of parking, don't tell the client to park in one place, then when he arrives and checks in, tell him, "ok, I'm around the block at xyz." If you've done your screening you should be at the point where you can give an address. Also on the parking thing, if it's a residence, make sure the address is easy to spot, driveway (if parking there is necessary) is clear and easy to access. Last, but not least, never ask a client to just follow someone else through a security gate.

 
A clean, dry, relatively modern bathroom. Nothing worse than stepping into a damp shower or stepping out onto a wet floor mat. If it's a residence, everything works well and is in good condition, shower isn't one of those cheap plastic/fiberglass remodel inserts.

 
Bottled water is always nice and a parting gift of a mint, small chocolate or similar.

 
For encounters over 1 hour, snacks (room service in a hotel) are important.

Sorry, I couldn't resist ... I'm such a bad typer that it makes me chuckle when I see other people's typos ... in your post you asked whether "convent access" is important at an incall location ... and I gotta say, I haven't once thought about accessing the nearest convent when I'm in the mood for a fun incall ...    And I guess the real answer to your question is that a sense of humor and a light-hearted easy-going relationship with the provider is the most important aspect of any incall location for me ... cheers!!  

Wow, that's hilarious! Oh man, I can't believe how funny that error is!

Literally LOL-ing  

Thank you for that!

LOL... nice replies! I might have to take notes. Also I always have water and I never offer shame on me ..
Where did my home training go? lol