Okay, so here's a scenario that actually occurs when I play live chess, and maybe it's wrong for me to do.
I've watched video's on particular openings, and I write down the recommended responses to various lines... example:
1. d4 d5
2. c4 dxc4
3. bxc4 nf6
Edit: I just read a comment I missed earlier, clearly this is cheating and so I won't do it anymore. Does anyone have any recommendations for how to practice specific openings so that I can get a good feel/habit of making the right moves so when I practice new openings I'm not just hoping they respond with one of the two lines I remember?
I think one way to look at it is that live chess is not really the place to practice. Of course, you can learn from your live chess games afterwards when you do the analysis. If you want to practice and play at the same time, I would suggest online (correspondence) chess so you can have fun and practice your opening at the same time.
That's a pretty clear example of note-taking, which is usually not allowed.