Hinduism is an ancient pluralistic civilization framework that is based on freedom of faith rather than faith itself. The uniqueness of the framework is that every individual has absolute liberty in choosing a path of worship and adopting or rejecting a belief system. Hindu civilization is held together by two profound philosophical concepts: Vasudeva Kutumbakam (the entire Universe is my family) and Sarva Panth Samabhava (equal respect for all faiths).
If an individual embraces these concepts he can be generally considered to be Hindu. There is no formal process of conversion into Hinduism nor is there a formal process of renunciation or excommunication. In the Hindu tradition there is an underlying current that draws you to live in harmony with nature and fellow human beings and therefore practices such as Non-violence, Yoga and Vegetarianism are widely popular. Anybody can be considered to be a Hindu irrespective of his or her belief system as long he or she does not explicitly choose to be identified as a part of another religion or tradition.
Hindus do not believe in proselytizing. Hindus believe that there are multiple paths to reach god. Hindus do not believe that one path is better than the other and therefore believe that every individual should be free to choose and practice his own belief system.
Thank you to Chandru Acharya