Easy there Bob! I've had one or two incidents in my lifetime.
For the most part I go to the same station and they know me (epsecially the Pakastani kid who is always is smiling because he smokes dope in the little booth!

)
All you have to do is get out of your car and stand next to him and ask him to be careful. The only thing to watch out for is not greasy hand prints because they don't touch your car (only unscrews / screws the cap), but rather, drippage when pulling the nozzle out.
Also, although you're not allowed to pump, some people do it anyway especially when busy and the attendant doesn't give you a hard time.