In a glass tank:
1.) Avoid using a ceramic heat emitter if at all possible, use UTH's instead.
2.) Cover the screen top of the tank with tin foil except for just a small area for ventilation.
3.) Use Cypress bedding.
4.) Use an oversized water bowl and put it on top of the UTH (I use the zoo-med reptirock - it is better for humidity on top of the UTH).
If all of those don't work, get sphagnum moss, wet it so it is damp but not dripping, put in bowls around the tank.
If that still doesn't work, put the sphagnum moss in a hide and just make sure the humidity in that hide is ideal even if the rest of the tank is not.