The common mistake that beginners make is to follow investment advice from people they don't even know that they read on social media or on bitcoin forums. The internet is littered with advice for crypto trading, much of which is from individuals trying to talk up the coins they hold themselves. These coins can even be part of organized pump and dump schemes in some instances. If you are going to follow someone's advice, make sure they are real experts in their field and not strangers distributing advice while hiding online under a pseudonym.