To me you tip people who are below your social stature. You tip them instead of spitting on them. So if you feel an urge to spit on them, tip them instead. Just kidding, of course. :) Seriously though, the only people I gnerally tip are people who rely on tips to make up their income. Waitresses, food delivery, bellhops, taxi cab drivers. That's it. Auto mechanics, rug installers, travel agents, hotel desk clerks, none of these people get a tip because they are simply doing their job as stated. The people that really annoy me are people like the Redcaps at and airport them you have one bag. They go to grab your one bag and I am placed in the awkward position to go "Hey, it's ok, I've got it". I don't know how we got on the trend of tipping 20% for merely adequate service, by the way. My default if it wouldn't make me a social pariah would be 10% for ok service, 15% for great service, for any bill over $20. Anything under $20 typically gets about 20%. When I eat at the diner for $6 it's 50%.
I used to tip delivery people actually, but funny story. I bought a 165 lb big screen TV from Best Buy. It came with free shipping. I planned on tipping the guys 10 bucks each. So two guys show up. It turns out that the entrace to the house I was living in at the time had this banister making it near impossible to move past it. The solution was to lift the thing up to about chest level over it then down again. Now both of these delivery guys were big guys with back braces.
So what do they do? They refuse to lift this thing over the bannister unless I pay them, get this, $50 EACH. I say, I think that's a bit excessive guys, I was goign to tip you anyway but you are trying to extoret me here, which I don't appreciate. They refuse to take it back or lift it. They leave the TV in my doorway and walk off, leaving it in a position where I can't even close the door and go to work.
So I called Best Buy and chewed them out. Bastards.