I used to tip all the time but less so now, I don't tend to carry much cash around anymore and the price for everything seems a lot more expensive, £18 for a haircut mostly cut with trimmers!! no way am I tipping that. I'll add 10% to food bills though.
I was in Boston last year and went to watch the Celtics, they were charging about $20 for a can of beer and there was a button on the card machine asking for a further 20% tip for the fella for opening a can, totally outrageous.
I only tend to tip somewhere if I really valued the service and there isn't already a 'service charge' on the bill. Usually roughly around 10% of the total and in cash.