I keep making the same mistake. How do you make intermediary planes?

Normally, I select a face and add a datum plane. It's button is in the toolbar with a the datum point and datum line buttons in light blue iirc.

That said, since v1.0, I've had far fewer instances of being affected, and have started doing some direct-on-face features (usually sketches) again.

This is described in the wiki page, at the section solution.