When going with a group, we will either request separate tabs right from the start so the staff know who to bill, or we will often pay the whole tab if we haven't seen a group for quite a while and like to treat.
There's nothing worse than either arguing or being embarrassed over nit-picking the bill or the tip. We have certain acquaintances who we know to be fussy over tipping, and go over the bill like an accountant at year-end.
We tend to have them over for dinner rather than meet them at a restaurant.
Canadians have now started to go more to the American method of tipping; now if there are groups over 6 the restaurant will automatically add an 18% tip.
When they hand you the credit or debit card terminal, the automatic choices are 15%, 18% or 20%.
We will almost always add 15%, unless the service is particularly bad, then we will reduce it or on very rare occasion, not leave a tip at all.
Remember also, the time to table in your case is usually caused by the kitchen, not the wait staff. And 20 minutes is perfectly reasonable amount of time IMO.
