Follow step 2 at the bottom to test your hygrometer. Once you get it dialed in that's about all you can do. You can always drybox a few days prior to smoking it they're too wet.
As far as hygrometers, I got a very accurate one years a go but using 65% beads pretty much keeps me in the clear. The beads are dead one (within 1-2%) and I know longer rely on the hygrometer.
http://www.sciencecompany.com/-W136.aspx