Excellent points! I had my undergrad graduation more than two decades ago, so get to appreciate some of these a bit differently from the twentysomething "younguns" here. If I had to pick two most important, I'd say point 1 (with the caveat that his point is generalized to all socializing) and 7 (maybe not so for US but for countries where parents play a huge role in shaping kids' future career choices).

I would also add time, that's the most important thing! When you get older you'll see that a lot of the breadth-first approach to life that you can do in your youth has now become depth-first, i.e. you won't have the time or opportunity to branch out to much. So experiment a lot when you're young.

That's what I would want my son to learn are the most important things, not just to get a good job but for everything in lide: maintain and build a good network and manage time choices wisely.