Ricki has had a problem with bedwetting, probably more due to our family's penchant for being deep sleepers than her Down syndrome. We have tried (courtesy of a pricey doctor) various methods to finish this matter, with varying rates of success. (No, we can not use a buzzer as the noise scares her and she flatly refuses to wear it.)
Last time we were at the doctor I told him, "DON'T speak to me. Speak to Ricki. Let's make this HER problem." And at home, I have religiously been making HER mark off (daily) a sunny sun or rainy cloud on the "follow up" records. Suddenly she seems to care more.
This reminds me of how I was able to get my sleepyhead son up for yeshiva (high school) years ago. I made it HIS responsibility. I purchased him an alarm clock that could wake the dead, and informed him that I was not going to awaken him. The next morning he jumped out of bed like magic. (And if he hadn't, one time being late would have done the trick as well.)
I am applying this principle in several areas of Ricki's life. She is receiving "natural consequences" to throwing things on the floor, etc. It used to be that evry time we went to her exercise class, she would throw away her hair band (used to make a pony tail), and we would travel home with her in a rather unkempt state as a result. If I asked her where the band was she would reply "I dunno." This week I called her bluff and told her that I would sit and wait until she found the band. Suddenly she "remembered" where she had thrown it, and fetched it out from behind several large pillows.
SHORT TERM this method can take a few more minutes (until they see that you are serious). Long term it saves you time, money, heartache, and energy.