You can register online or by phone or by mail. The detailed information about registering for the GRE can be found at www.yocket.in
Extracurriculars are always an add-on to your profile. Any achievements at the state or national and international level are considered important. Working for social causes such as for an NGO or charity trusts on a regular basis
Some are clear about their universities, but not sure about which and why to choose any particular course. There are some things people know, so ask them right now!