Ways to optimize voxel generation like Minecraft

Let me get something straight first; I don't need it exactly like Minecraft. I just want to know how they generate millions of blocks on screen without serious fps issues. I know of chunks and im trying to incorporate that in my own way. Right now i can get about 900 blocks at 40 fps on my gtx 560 ti card, which is pretty terrible. Blocks render depending on player's distance from the corresponding chunks.

I know that Notch uses some sort of occlusion culling that keeps certain faces from rendering if they arent next to air. However occlusion culling is a pro feature, and I'm not sure if it culls on a per face bases. Unity's batching and frustum culling is the only thing in effect that seems to be keeping the fps from being at 0.

So how can I "hide" faces that are touching other blocks? I don't need a whole script, I just want a snippet or pseudo code that demonstrates how to access the faces of a mesh and set them to render.

Also what are other methods used my Notch to be able to render all those blocks without fps problems?