What kind of substrate do you prefer?

[Vypyrz]

I use Aspen Sani-Chips. I like it because I can spot clean it, plus it is cut up so small that if it is accidentally injested, it won't stick or cut their mouth and is easier to pass through their system.

I forgot to add that it vacuums up easily if you spill it. It doesn't stick in the carpet like shredded aspen does. If you decide to use the Sani-Chips, I suggest using a plastic cup or something like that to scoop it out of the bag.
I get mine from a vendor who sells it at our reptile shows.

How deeply do you keep your sani-chips/aspen shavings?

I usually keep my substrate layer somewhere between 1/2" to 1" thick.