In our house, everyone (me, DH, 14-yr-old twin boys) is responsible for making sure things get done around the house. In the summer when they are home all day and DH and I are at work, the boys get a list each day. By the end fo the week they will have mowed the lawn, cleaned up dog poo, done a couple of loads of laundry, put away their own clothes, vacuumed, brushed the dog (he gets walked every day), cleaned their bathroom, loaded and unloaded the dishwasher, and cooked their own lunch. They also practice their instruments (almost) every day. Once a week they clean their Grandma's apartment (for pay).
If I have time, or if I just feel like it, I'll mow the lawn. It's not specifically "their" job - it just has to be done.
During the school year, DH and I take on more jobs, because we are all gone during the day. The things we ask them to do depend on how much homework they have and what other activities they have on a given day (Scouts, church).
In our house, if we ask the boys to do something, they do it - not because they have a certain number of chores to do each day, but because, as members of the household, they are partially responsible for these things, and that has always been the way we've operated, so it's second nature.