So I'm just starting to learn the CK, and I'm going through the video tutorials. When the guy in the video adds a new tile to the render window, it appears at the z-level he's working on. When I do it, it appears at the z-level of the camera, meaning I need to spend 30-60 seconds per tile trying to make it match up properly. It's driving me mad, and putting me off learning to mod entirely. How do I make it behave better?

drop it onto an existing item, not next to it. So if you're putting down tiles that have a floor, wall, and ceiling, put down one piece (first one) and then when you put in your 2nd piece, put your mouse on the floor of the previous piece. The 2nd piece's floor will align to that Z-plane.

There may also be a setting you can choose in the options - I can't recall for sure - where new items are placed at the center of the world space. I may be thinking of another program entirely, though.