What should i do to go into playback singing field?

Firstly you need to have the passion which helps you to reach ur goal. Secondly, get a Guru/teacher for yourself, do persistent practicing. If you think you are well versed, give a shot at any of the singing reality shows and please do give your audition to any of the renowned music directors. Good luck

Hard work , Patience, Music-Networking and a little bit of luck is what would help a lot. All the best.

First of all you need to practice as much as you can to be an expert in your talent and also it's important to have the same best singer's mindset. Success in any area depends 85% of your attitude or emotion intelligence and just 15% of your formal knowledge. Regarding playback tech, in google you will find free tools to start use functionality, but it's important to focus also in best tools for this kind of filed. Good lucky.

Based on your question, I understand that you choose to consider your career as playback singer and not just a part time hobby.

According to me, the prime requirement for a playback singer is to know basics in music. I assume you already have it (completed some levels in for ex: Carnatic music ?) If not already done, you should be starting here.

If you already have the prerequisites and only need a breakthrough, then the best thing would be to start recording yourself some karaoke songs and upload them on social networking sites (youtube, Facebook etc). For pre-recorded music tracks there are several Mobile apps that you can make use of. This will also help you grow your network with similar set of people.

I know couple of my friends who have followed the same and are now into setting up strong base as a playback singer.

Good luck to you.