Best practices for 2011 Mac mini connected to monitor + HDTV?

Your "best practices" will depend a lot on your usage and expected behaviour. It sounds like your preferred option would be to keep both plugged in, but have an option to disable one display at a time. Unfortunately I've not found a way to do this, but there are a few tips and tricks you can use to make things more manageable.

The first is Gather Windows. It's an option in the display preferences that will move all open windows to whichever display you click it on (you get one window on each display). Useful for switching between displays.

If you use VLC, you can set a default screen to use for fullscreen video, under Video > Fullscreen Video Device and choose a screen. Then no matter what display the video opens on, when you full screen it, it will jump to the screen of your choice (presumably you'd set it to your HDTV).

Finally, you may find Moom useful. It's a great $5 app that gives you a bunch of window management options. You can get a demo to check it out. You can set hot keys for actions or use a nice pop-over that appears from the Zoom Titlebar button. Very configurable and useful, I suspect it would be handy in your case.