Pretty simple process
1. Have a GOMTV account
2. Log in
3. Go to http://www.gomtv.net/event/GSL3YearAnniversaryEvent.gom
4. Leave any comment
5. Grats you have a free three day ticket for GOMTV that covers all current SC2 leagues, as well as all past SC2 leagues. This also gives you EHQ quality for everything, the equivalent of the premium ticket.
6. Go watch stuff you haven't seen or can't watch live because of timezones
Recommended game list from last year's thread here: http://www.teamliquid.net/forum/viewmessage.php?topic_id=365715