hi,,
Today, all adultsabove the age of 18have their right to vote their own representatives in the goverment. Representatives are elected on the basis of how they will work for the welfare of the people.
In Janapadas, the rulers were chosen by performing big sacrifices like Ashvamedha (horse sacrifice). Shudras were not allowed to attend these rituals. The rulers were selected on the basis of their strength.
I hope that this is the answer to your question....