In restaurants I tip between 10 & 15% depending on how good the service has been. I always check the bill though, if a service charge has been added, I have that removed and give the tip in cash to the waiter/waitress!
Just once, when the service had been slow and the waiter was extremely surly and offhand, the tip I left was written on a napkin (a fabric one to boot!), and said 'Part of your job is to smile, if you'd tried it with us you'd have £9-00 cash in your pocket instead of nothing but this note'!
I appreciate that there are times when staff perhaps don't feel great, or are tired, or worried about something, but having worked with Joe Public for 38 years and never once failing to smile and be friendly, every damn day, I get very cross when I don't get the same treatment as I always gave!
At Christmas, postman and window cleaner get £25-00 each, bin men £30-00 between the three man crew. Our postman, Pete, is wonderful, and thoroughly deserves his 'tip'! The bin men get a tip because they do a horrible job that I'd hate to have to do! Our window cleaner is a lovely young lad, he works for his girlfriend's dad, who takes 35% of the takings every day! He's like a little monkey, up and down ladders in a flash, makes a brilliant job of the windows and earns very little for doing it, so a decent tip makes up for some of his lousy pay!
I take boxes of home made biscuits into the hairdressers, bank and Drs at Xmas for all the staff to share!