There are three live shows of the Eurovision Song Contest 2012 this year, the Semi Final 1 on May 22nd, the Semi Final 2 on May 24th and the Grand Final on May 26th.
In some countries which do not participate in a particular semi final and all the non participating countries there won’t be a live broadcast. Sometimes it will be even shown time delayed. In these cases internet live streams are available.
So wherever you are in the world you will be able to watch all three live shows on broadband internet. You can follow this on the official Eurovision.tv site: http://www.eurovision.tv/esctv/future