The only experience I have is with a terminator model. I came with instructions, but basically all you do is wear it for as long as you want. I know some people wear them 24/7, but I prefer to just wear it during the day and since I like to sleep naked I don't wear it at night. I can wear it under my clothes and no-one even knows it's there.
As for whether it works or not I can say this for sure. When I wear it I notice that my bm's are freer and more regular (a good thing). I stopped wearing it for a week whilst I was moving house. It got packed and I just forgot it. I noticed on those days that I wasn't wearing it that I had less energy and actually took a granny nap each one of those days. I put it back on yesterday and found I had more energy again and didn't need to nap.
I haven't tried those other cheaper models that use the 20-7-20 or whatever timing. They just seemed too confusing to me. With the terminator I can wear it for as long or as little as I like (although they recommend a minimum of 20 minutes at a time).