Product review (5 stars): Best Way to Humidify your Cigars
If you have a big investment in cigars, you must have these.  Keeps the humidity consistent and no messing around with gels and water.  If you haven't used before or have a humidor with less than 100 capacity, you might want to consider a smaller pack.

Just throw them in and forget about it.  May take a week or two for your humidor to stabilized if you haven't used before, but it will get there.