Just received email today from OSCP saying I passed the exam. There are plenty of good advice regarding knowledge and skills on this or other forum and I won't repeat them here. But I have one non-technical suggestions from my own experience and hope it can help other guys.
Don't hesitate to revert the machine when you feel confident about your exploit code should work. As I rarely reverted the machines in HTB, that habit almost killed me in the exam. I spent almost 3 hours working on my last machine as my exploit code doesn't work, so I spent all the precious hours to look for and test other exploits. As the last resort, I reverted the machine and found the previous exploit code works!
Also, a big shout out to 21y4d, and I used his nmapAnimator script in the exam, it saved me a lot of time.
Lastly, hope you guys all pass the exam very soon!