question about blind people and guide dogs

[sneaky]

I'll start by saying this is a serious question that i want to know the answer to and i figured it would be better to ask here rather than ask a random blind person in the street.

Ok so, a few weeks ago i started catching the train to and from work and noticed a blind lady with her dog at the station a few times. This got me thinking about how you train the dogs to know where the station is.

So the question is - how does the dog know to get to the station from home, or which platform is which when they get there?

Probably a simple answer, but i'm amazed by the owners and animals