Which usually means my car key and the required amount of cash. Wallet, phone, etc. stay in the car. You can't lose it if you don't bring it in.

Way back in the day when I saw SWs, I would have the cash I need for the session in one pocket, and my ID in another pocket.

If I am TOFTT with a new gal I don't know, I will have the fee, plus maybe a little extra cash in a different pocket, just in case I feel like tipping, or buying extra time, or maybe an additional service (yes that would be an upsell but I'm not of the belief that ALL upsells are bad), my ID, and probably my phone.  

If I am seeing a well reviewed lady or someone I know well from multiple visits, then I will have my phone, my entire wallet, and everything I normally carry on my person, plus sometimes an additional bag or backback.

Usually only bring my wallet if using public transportation to get to the hotel.
I also sometimes bring a small gift.

...with the exception of the donation, which I keep folded in my back pocket. I just make sure that my pants are always with me at her incall location. They are never out of my sight. Even after a "before" shower I will take my clothes with me out of the bathroom and leave them on a chair or other location in the room with me.

...envelope.  

Seriously though, I have my burner phone, keys, cash, and ID...  

and let's not forget, my rapier like wit, and awesome smile. LOL

I usually also take my cell phone with a playlist of the the music I like. Providers seem to like that. I also take a couple of condoms that I like to use.

You wouldn't  leave your wallet in your car if you went to the mall.  I bring my own equipment if I'm not seeing an ATF.