I've done my time in the service industry (waitress and retail in high school/college) and was taught as well -- always say please and thank you. It's 'May I?' rather than 'Can I?', and certainly not 'Give me...'

I find myself saying thank you to the fast food employees. It's amazing how many of them actually smile and give good service once you do that. Courtesy begets courtesy.

For every please and thank you I give, I like to think I've helped others to do the same... let's keep the tide rolling!