Rebuke/ Judgement

Where do u draw the line between a rebuke and a judgement? If you are to love your brother, you would do whatever you can to lead him back to the path of righteouness. But being mere humans, who are we to know that we have not strayed from this path ourselves? By telling your brother what he should and shouldn't do, do we not just committed the sin of passing judgement on others? So, where and how is the line drawn?