Oh yeah, you really can't get too tied up in looking at each and every reference point if you've got a ton of them. If I looked at every one of mine I'd get nothin done! :p You gotta build the "rp catalogue" quickly and efficiently in a way that it helps you get around the track, but doesn't hurt you by getting you too distracted and overwhelmed :dizzy:
But like you said; braking, turn-in, apex and exit are obviously by far the main ones to be concerned (with which is why there's usually cones out there to give you approximate locations of each) and having additional ones is definitely important to building consistency, especially as you get faster.
I've ridden at tracks elsewhere (NJ, NY, and VA), but having done track days & races at NHMS for the better part of 6 years now, Loudon is the one I have the most experience at BY FAR.
But I've also been in the position a couple of times where I had to teach at a track that I've never seen before that day...
To prepare I'll talk with others who have been there, check out track maps & watch whatever videos I can find of the place... AMA or club races if I can find it or just track day on-board stuff on Youtube. Of course I keep in mind that what lines they're taking may or may not be "right" but it certainly does enough to help me prep at least a little and get a better idea of what the track is like.
Before the first session of the day the staff gets together and does a few follow-the-leader laps of our own, riding nose-to-tail at an easy pace that allows us to look around, see the track in detail and note where the line is on key parts of the track.
When it comes to certain sections, sometimes I like to pick fixed points off in the distance away from the track surface to aim at, like buildings, tall trees, tire walls, etc.
Nothing out of the ordinary.
But actually, what really helps me most is the
Ben Spies method
That's the key, right there........ seriously. It really helped me a ton at Monticello North (Dolpin) and NJMP Thunderbolt (Dodo bird) and I now have over 600 key chains.