At the beginning, when Cheryl and Randall were at the wedding, Randall kept on being a but hole to Cheryl. Being mean to a sibling is a BAD thing.
Randall was trying to sneak and get Vera's journal so he can do a prank with it, but then return it. If someone is sneaky then stealing something that is a BAD thing.
When the whole Shadow Club group was getting revenge on Tyson, the only person who didn't show up was Randall. Instead of going with the Shadow Club group and doing things he signed up for, he decided to go do something else important that was not important. If someone wants you to do something and you even signed up for it, then you should go to it. Even if it is not important to you. That is a BAD habit you can have.