I think back to when I was a kid in high school working in a grocery store for minimum wage. When someone gave me a couple bucks for loading thier groceries which was my job. It made my WEEK. That was awesome. If I got 5 I was estatic. That was a burger, frys and a drink and money for a snack on my break.
My wife says I tip to much, which I tend to do. Still I know a couple extra bucks to a waiter is going to help them pay an electric bill. To me it will get pissed off on a soda or something useless.
I generally tip any service person that I use on a regular basis. When my truck pulls up to the Oil and Lube it doesn't matter if there are 10 cars in line. Mine rolls right into the stall that opens next and I get A+ service because the guy nows my truck and knows there is an extra 10 bucks waiting for him for lunch when he does a good job for me.
If I call the Dr I get in that day because I have sent flowers to the receptionist or dropped off sandwiches for the ladies in the office for getting me in the same day when there is a 3 day wait. A nice gesture pays out 10 fold. If nothing else I always let people know how grateful I am for their help and spending the time to give me good service instead of just taking my money and going to the next person. On the flip side if I get piss poor service I take the time to let a manager know that also.
Blake