I used to be a Valet. The person that opens the door for you is not in most cases the one who parked your car. they are the "control person" They keep cars and guest flowing at the entrance. they may move your car to a line, where "runners" take cars back and forth to the lot.
most of the time Your car at drop off will sit until some wants to pick up a car. This way we can drive back and forth instead of having to run.
A valet should not expect or demand a tip. They should never hold there hand out for a tip. A tip is a kind expression from the guest. a .25 should be recieved with the same graditude as a $5 bill.
Tips are pooled and it does even out. The normal tip still today is 1-2 at pick up. Valets are min. wage to $8 per hour position.
Some guest do not tip at all, and some guest tip at the end of their stay. They may come down to the desk and give the captain a $20. Sometimes they may say to us, I'll make sure to catch you next time.
A good valet should be reading your name on the card in the window and address you by name when they drop off your car.
Anyway, tipping should be what you want, not what is expected.
If you feel comfortable with no tip, then that is your right. You will get the same service. If you give 1-3 then that should be fine. If you worry all week that you are not giving enough, then give what you are comfortable with. An extra dollar or two is worth it to keep your mind at peace.
If you give 5-10 dollars, then it goes in the "other pocket" and a 1 dollar bill gets dropped in the pool.

(thats a little valet trick)