Here's a very important tip I learned the hard way. When you hit the extrude button, it does an extrude even though you don't move it, so be VERY careful with that. The extrude will occur, even though the new vertices are in the same places as the old ones, and you'll be stuck with an extra set of points...NOT UNDOABLE if you proceed to model like this. Like today I had to start a whole spaceship from scratch because I extruded a whole bunch of polygons and didn't know it.

What's cool though is that you could delete vertices and edges without ruining the mesh, not like in Max. Bomb diggity.