I tip for service, the amount depends on how good I think you did and the circumstances. There's times I've given $0 and times I've doubled the amount of the bill. Often enough all it takes is a good personality. I have tipped for take out but it's not a standard I keep, same for a buffet. You gotta make yourself stand out a little and show you have a little more ambition than just showing up.
Beware of any old man in a profession where one usually dies young.
