We use priveledges as motivation here - and removal of those priveledges if their chores are not done. This seems to work well for us (our four children range in age from 9 - 16 years old.)
For instance, one has the chore of sweeping the dining room floor, 2 of them share the responsibilities of doing the dinner dishes, the other one cleans the living room and takes out the trash. If they don't do their chore, then they will either get: no TV for the night (and that means no video games, which they really enjoy playing) - or if they give a lot of grief and/or backtalk and resist doing their chore - they will not only have to end up doing their chore, but will also have the "pleasure" of doing one of their siblings chores for that evening as well.
