There are instructions for an inexpensive, homemade incubator here. Vermiculite is a favorite incubation substrate. A layer of spaghum moss is sometimes added. Both of these retain moisture very well. Spray water to moisten well.
High humidity is essential.
Substrate must be quite damp, but not in standing water. Incubation temperature seems to determine the sex of the hatchlings in many reptile species. 82 or lower may be expected to produce mostly males. 86 to 90 degrees would possibly result in mostly females. 83 to 85 degrees should result in an even mix of boys and girls.