Hello Pranavi,

Start with volunteering.
Great politicians around the world had their start volunteering for a cause they were deeply committed to. Mahatma Gandhi, for instance, started volunteering his time to get Indians in South Africa some of their civil rights. A variety of other Indian leaders either grew up participating in the freedom movement or one of the various causes that came later. 

Barack Obama was volunteering for a church organization in tutoring students and doing other community work. Later he worked on a project to bring unregistered African Americans their voting rights. Narendra Modi got his start campaigning for civil rights during India's Emergency in 1975. Bill Clinton got his start during Vietnam war protests. 

Aspiring politicians should start with such volunteering. Ideally start with something other than a political party to have some clear successes to add to your resume. For instance, you could devote a few years of your forming years to a literacy project. That would give you insights into people and also some successes that you can show.

Study Law.
A lot of successful politicians come from the legal background. This is because a lot of us non-lawyers have little patience for understanding politics and doing compromises. We tend to get onto an imaginary pedestal when talking about the politicians. This idealism leads to a naivety that eventually destroys careers.

Lawyers understand political systems and people better than an average citizen. They work on compromises and practice a lot of time arguing and negotiating. 

Take leadership roles.
Great leaders took a variety of leadership roles in their run up to the top. Can you lead a project in your locality achieving something critical? For instance, if you are able to lead a handful of volunteers in wiping out illiteracy in your street in India, you could get increasingly bigger opportunities. People love leaders who succeed in their job.