Below are the common mistakes a project manager does,

  1. Not clear on the requirements
  2. Improper planning and not setting up proper priority for the tasks
  3. Dependencies are not gathered/ addressed on time
  4. Missing on documentation
  5. Not managing proper expectation with client or stake holders
  6. Being reactive rather than proactive
  7. Not tracking the status of the project regularly/ once in a while
  8. Not planning on Risk Management
  9. Not maintaining a proper communication among the stakeholders of the project
  10. Not monitoring or maintaining the budget of the project to run in profitability
  11. Being Resistant to Change
  12. Missing to recognize and not encourage the team for better performance
  13. Being too liberal with the team members
  14. Allowing the scope increase
  15. Not being transparent with the team/ client during crunch situation and not informing the client when there is a bad news

If you have any points then add the same in the comment section.