The 3 things you shouldn't do in trading in my own opinion are
1. Don't trade if you don't know what you are into - Be informative on the latest happenings in the market especially if you aiming to buy some alts there a good research is needed so that you will not fall on dead or been trapped on dumped coins.
2. Never listen to the fuds sometimes there are sick people who spread fud news just to create panic to the newbie traders and if you been caught by them for sure you will miss the gold(profit) times or worse you lose your money.
3. Hand your money to the people who said they will trade for you and you will earned a percentage daily since a huge possibilities that they are 100% scam.
Exactly, this is what most common people does is that they are believing in any kinds of FUD, once someone said, 'this project is scam' or once the project's coins or tokens dropping its price a bit, the panic with it easily and will ask for a lot of questions, why the price is dropping, they didn't realize that it is just a way for other people to make them buy more at cheap price.
To many something like that especially if you are reading the chat box of certain exchange(some exchange having this option) and also in telegram groups and other social networks. But for me I don't listen on those since I'm on my god feel and visiting the official channels of the coins if I wish to hold them for more little longer.