This depends on the species of tortoise you are breeding. For my Russian tortoises, I follow @kanalomele 's advice and keep the vermiculite bone dry, and place a container of warm water in the incubator next to it. Even with high air humidity in the surrounding, i would still keep a container of water in the incubator, since the heating element does otherwise dry out the air. Using this method, I've had close to 100% hatch rate - the eggs that haven't hatched were not fertile to begin with. Folks who use moist substrate seem to often end up with cracked eggs or funky fungus issues.
Depending on what species you are trying to breed, this may differ though. For example, redfoot torts need moist substrate, I believe.
mine's star eggs. i read the incubation techniques thread here it states:
relative humidity sustained at 70-80%
1.2:1 ratio water to vermiculite by weight
im not sure if i need to do both. or does it mean to do the damp vermiculite to achieve 70-80% humidity. since my air humidity is already in the 70-80% range, having damp vermiculite will definitely be in the 90s.