FInding a guru

Lama Surya Das talks about his own journey of finding a guru in his life featured in his book "Make Me One with Everything: Buddhist Meditations to Awaken from the Illusion of Separation". What is a guru? How does one know if they have found the right person? What differentiates good teachers from ones that are bad teachers. https://youtu.be/YH9UCmUmO24