and think it also depends on what type of car you have and Where you are.
If it's a regular place that you go weekly like a restaurant or Club, you Tip both ways. and again is it the same guys all the time ?
When I go to AC, I will tip both ways. Because it won't be the same guy from when you check in, and leave say... 2 or 3 days later.
Which brings me to the other part, How much.....
The place I get my Hair cut has Valet, I only tip them $2
There's a few restaurants that I go to, either Weekly or bi-weekly. Been going there for 15 years. depending on who's working, they can get $5 or $10 both ways