The idea is you get two jars, and you fill one with the same amount of marbles/gems as you have pounds to lose. As you lose weight, you move the gems over as a visual representation of how well you are doing, or maybe it can act as a a little gee up if you're not doing so well! I have already lost 14lbs so I moved over 14 little gems into my "lost" jar. I still have 28 gems in the "to lose" jar.
My plan is to weigh myself once a week, and move the gems accordingly. Hopefully I will only be moving them one way, but if the worst should happen and I have to move some back into the "to lose" jar (going on holiday next week...) then I have that motivation to really get back on it as soon as I can so the jar looks better and better!
Here are my jars so far! Hopefully I can post a picture soon with a visual update of some good progress!