One of the things that has been most effective on my boys as they've gotten older is this: I ask them to do a certain job - mow the grass for instance. Then if I have to remind them again, I just say to them, "if you are not going to do it, just say so now because I will go ahead and do it myself if you're not". Only one time have I ever had to actually follow thru on that threat. I had told Keith to mow and he didn't get to it. I told him twice and then finally said to him that he could forget it - I would just do it myself. He didn't believe I would. So I started the job myself. He looked out his window and saw what I was doing. It took him about 10 seconds to come running out and offer to take over the mower.
guilt is a wonderful tool