Youngsters usually have ideas about jobs they would like to take on, once you open up the possibility to them. And nothing is better than getting their ideas, encouraging them to think, and listening very seriously to what they have to say. I can't pass on any fail-proof tips about how to make a child's chores and responsibilities around the house always work out well. But I do know a few general guides that may be useful to you. A schedule and regularity really help.
Company helps, too.
Children are more apt to stick by jobs they can do with someone else, rather than with the lonely jobs where they are off by themselves. Praise works much better than criticism to keep children going. Some people wonder, incidentally, if they should pay their boys and girls for the jobs they do around the house - perhaps a penny or a nickel or a dime. I think this has to be each family's decision. But I do think even young children benefit by having a small allowance, money that is theirs just because they are in the family, money that is theirs to do with as they will.