basically you can follow two paths in this. you can go either by local sighting or by global. If you go by local sighting then you are looking of the moon in your own city. If you go by global then you go by anyone who first sees the moon.
Going by local sightings doesn't make sense these days. For example, ISNA and other US Islamic organizations are considered "local" and they decide for North america. Now you tell me how all of canada, US and down to mexico is considered local? how california to NY is considered local? Some people just want to feel in power and thats all.
We all should follow global sighting as its easy to communicate across the world. And the prophet (saws) said when you see the moon, then fast. It's the same moon, so why is everyone hunting for their own moon?
So how is it that everyone is fasting the same day this year? There was no sighting of the moon anywhere in the world, no one was able to see it. When you don't see the moon then you complete the month, thus sha'ban had 30days and next day (thursday) would be 1st of Ramadan.
anyways, people can go local or global for ramadan but they have to global (with saudi) for Eid Al-Adha. Even then many in the west try to look for their "own" moon. Adha is convected to the hajj. And hajj is in saudi. So everyone has to go with the hajjis and can't go having their own eids.