Hi Ashish, glad you want to get involved with Tor for GSoC! The first step would be to look over the projects that you're interested in, and try to make a small contribution or two. George is the maintainer of Obfsproxy (asn on irc) and I'm the maintainer of Stem (atagar on irc).
Here's some links that might help you along your way...
https://www.torproject.org/getinvolved/volunteer.html.en https://www.torproject.org/about/gsoc.html.en
... and some stem specific information...
https://stem.torproject.org/ https://trac.torproject.org/projects/tor/wiki/doc/stem/bugs https://www.torproject.org/getinvolved/volunteer.html.en#stemUsability https://www.torproject.org/getinvolved/volunteer.html.en#stemTestingForTor
Cheers! -Damian