What questions should people ask themselves when deciding if they are a leader?

Do you lead for a cause or for self-gain?

Even though it is important to have ambition, a good leader dedicates their energy for a cause, then for a team, and finally to make themselves happy, if at all. 

Being a leader comes with power, but that isn't the only defining characteristic. If you take on something wanting only self-gain, it will be evident in its outcome and be reflected on your team.