@naomi24: When you receive a letter signed by a friend of yours, you know who it's from. Anyone could ask you: How can you be sure it's from your friend? It might be someone else. However, you know, from the content and the style, who it is from. Also, the person tells you their identity.
So, when information comes from God, He often tells you who it is coming from. And the style and content show that it is from God.
People pooh-pooh the idea, and think they too can make predictions, out of their head. A few might come true by sheer coincidence. In the case of a person receiving information form God, on the other hand, things foretold come true consistently, one after the other, and this is what removes the possibility of coincidence.
I highly recommend you read the lecture that I gave the link for. And here is the link to the book "Tadhkirah", the collection of dreams, visions and verbal revelations received by Mirza Ghulam Ahmad, in India, who founded the Ahmadiyya Muslim Community:
http://www.alislam.or...y/books/Tadhkirah.pdf
It shows vividly how the phenomenon of divine revelation occurs with regularity in the case of highly spiritual individuals. I hope you find it interesting.