1. Do not remember electronic wallet password
2. Do not back up your wallet
3. Do not research new services
4. Buy and sell based on feelings
5. Leave your money in the electronic money floor
6. Waste time on faucets (we all did)
7. Collect dust and pay high fees on it
8. Leave coins in an exchange
9. Trust the wrong people and get scammed
10. Panic at a price correction
Well, we all make mistakes especially as newbies. I wouldn't be where I am today if I hadn't make some of those mistakes. The best part about is learning from it. This is a good way of educating the bitcoin users, and I think this applies to all not only the newbies - experience is the best teacher. This should be a reminder for everyone as well, and no matter how long you've been using bitcoin, its always to good to keep learning.
I'm definitely guilty of number 6 and I regret wasting so much time on it. It's one of the reasons why I got discouraged and lost interest on Bitcoin some years back.