Hello Rish and welcome.
As Kev has pointed out, the ethical side of things is very important. On the technical side it would help us to know what kind of networking background you have. If you have none, then I recomend you start off with an intensive study of TCP/IP. Go to this link
and read through it. Click on all the links there and read through those too, particularly those at the end under "External links".
A good understanding of OS's won't hurt either. Know Windows and also UNIX and/or Linux. A good place to start studying UNIX is here
CEH, CCSA NG/AI, NNCSS, MCP, MCSA 2003
There are 10 kinds of people, those that understand binary, and those that don't.