In the word ‘Guru’, ‘Gu’ means darkness, while ‘Ru’ means light. So Guru means the one, who removes the darkness of our ignorance with the light of his knowledge. Merely by giving out a ‘mantra’ or tying a sacred mala on your neck, one cannot become your Guru.
According to Shrimad Bhagavad Gita, a Guru should be a knowledgeable follow the path of Vedas shown to others as well as realised the Supreme Truth by treading on this path. Being knowledgeable implies that the guru should be proficient in Vedas and scriptures, only then he will be able to convince you and show you the right path in accordance with Vedas and scriptures.
Only such an enlightened person can inspire you and give you a new direction in life. The ritual of providing a mantra and sacred mala comes much later, similar to a marriage where the bride is given a mangalsutra to wear.
Through the provision of the mantra and its repetition, a process of purity and strength begins in the mind of the spiritual aspirant and through the guidance of one’s sadguru, one’s upward spiritual journey commences.