Tipping a limo driver?

[jennydep]

Friends have hired a limo to take us to and from our airport for dd's wish trip beginning Saturday. We've never used a limo before. How much do we tip the driver?

Thanks!

 

[ducklite]

20% of the cost of the limo. If it's one way, then 20% of that. If it's r/t then 10% of the total cost each way.

Anne