Tipping Concierge-How much?

[mommytobug]

Does anyone know how much to tip a concierge or are we supposed to? We are going to Chicago and he has scheduled a car to pick us up at hotel and has answered a lot of questions. Do we tip? How much?

 

[John VN]

Just did a search under Tipping Guide and it has $2.00 to $20.00 depending on circumstances.