Amber,
After some really bad experiences hatching and subsequent consulting with others, I now use the dry hatch method. My results from hatching have improved dramatically.
Basically, I add no water for the first 18 days of hatching. The humidity levels, for me, will fluctuate from 16-26%. This allows the eggs to lose a necessary fluid volume. This has several positive benefits. The air cell needs to grow large enough for the chick to pip into and breath air. If humidity is too high, there could be water build up in air cell. If the chick pips into this, the chick will drown. The second major benefit is "wiggle room." By allowing a larger air cell to develop, there is less space for the chick to grow. This prevents the chick from getting too large and then become unable to turn effectively and zip its way out of the shell.
For temperature and humidity indication, I use a local digital instrument and another digital one that transmits to a remote location (my desk), as well as an old fashioned thermometer. Good luck with your hatch! I always get excited on hatching days. It just seems to bring back that wonder we experienced in our childhood days as new life comes into the world.
Tony