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.