Hey there,
I’m sorry if theres a painstakingly obvious solution to this question, but just looking at the menus hurts my brain a bit still, I only started using zBrush (and 3D modeling programs in general) today.
Anyways, I’m going through the tutorial videos and the guy’s tweaking the Initialize settings for the 3D meshes (like the 3D saw), and whenever he tweaks something it automatically gets applied to the mesh he has on his drawing board. But when I try to do it, I have to make a new mesh on my board to see the difference.
How come? Do I have some sort of automatic application setting turned off? Help, please? Making new meshes all the time to see what’s different is getting really annoying! 
Thanks!