Ok,

I was able to contact a concierge concerning an upcoming stay and he was able to both provide me with tourist information, but also has made (at my expense) arrangements for a limo and greeter to meet me at the airport.

I want to thank this particular fellow and his assistant concierge, but I don't know the proper policy for doing such. Would a twenty dollar bill in a plain envelope be acceptable? I know that people with that position are supposed to answer questions, but I think it was really nice of him to help me with a car service.

What's the best way, not violating a social norm or breaking rules to compensate a staff member? Cash? Box of candy? Sending an email to the GM? Half bottle of Glenfiddich?

Chuck