I've worked on this for years. LOL Still working on it.
When little, I had penny or bean jars and they earned beans as a positive reinforcement. They'd get to choose something to do as a family when they got to so many beans.
I don't do allowances because I think learning to just DO things is important.
A member here told me about putting laundry in a basket on Wednesday and saying that if you want to do video games on the weekend, you need to have that put away by Friday.
My 7th grader is under a lot of academic stress already! He is quite academic and has high expectations for himself -- plus his developmental delay which makes him a little slow at doing homework . . . he's got almost NO downtime all week long until the weekend. Between school, sports, scouts and band. I genuinely feel bad for him sometimes--- but can't really see myself saying to not take school and the other things he does less seriously. But it leaves less time for the jobs.
I struggle with this, can you tell? LOL
As they got older (after the age of 6), I'd give them something to do and then let them decide when to do it. "I'd like you to clean the mouse cage today, doesn't have to be right now, just please work it into your day, they really smell" and then make it fun by locating a couple used cardboard food containers to make a mouse fort tunnel for them in the cage. "You need to start your book report today, it's due in a couple days, let's sit and start" and then offer them cool markers and sit with them with a snack to get started. With my youngest, we did "lemon math" which was practicing math skills for 10 minutes, and he got to set the timer which was in the shape of a lemon. "Ding" you're done! The key for me was keeping things light and fun when there was a job they needed to do. I was in a fabulous play group when my kids were little, and it came to us as such a lesson watching how HARD kids would work to do something they wanted to do. Build a creek dam, bury a friend in the beach sand, etc. If they wanted to do the task, they would work very hard. That was the goal - to make them want to do it.
First, make sure that they know how to do what you want them to do. You do that by doing it with them over and over again. Make it a game.
Once they can do it - it depends on their age as to how long they keep doing it. Doing something because it is a sense of family/responsibility is always longer lasting then just a reward. The problem with rewards, is sooner or later, the reward is not worth it to the person.
And, of course, keeping the task to a time relevant to the age of the person is important.
Finally, (well, not really) praise is really important!