I used to be confused about the judicial retention ballots in Illinois. Essentially, a judge stays in until they lose a yes/no vote.
I am confused no more. A friend explained that he always votes "no". Generally, there are a lot of people who vote "yes" on a knee-jerk basis, so it is hard to get mediocre or bad judges out. By voting "no" where you have the slightest doubt, you are raising the possibility that a bad judge will lose the retention election, while not really increasing the probability that a good judge will lose.
Just vote "no" if you don't know any better.