Loved this article. I'd add a few things I wish someone had told me when I was starting my PhD: 1) Maximize variance, but know when to stop. Karpathy's point is great. Explore early, say yes to different things. But at some point you need to pick a direction and commit. Too much variance and you end up with nothing solid. 2) Consider smaller labs. Big famous groups are tempting, but in a small group of 3-5 people your adviser actually knows your work and gives you real feedback. In large labs you can easily become invisible. 3) Collaborate outside your lab early. Don't wait, reach out to people at other universities working on related problems. Different groups think differently and that's where good ideas come from. 4) Visit other universities. Even a few weeks at another group forces you to explain your work to people with different assumptions. It's one of the most useful things you can do during a PhD. 5)Learn to write good, structured, reproducible and maintainable code. One of the things I regret I didn't, and many working hours were wasted.

Good luck to anyone starting out.