How do you know the God exists?

I personally believe that we have a creator and the God exists. But how can you be sure? There are times that I get suspishious. Thats the time I look at sky, the stars and think how vast is universe. It is mind blowing. Thats enough proof for me to know that this vast unuverse has a creator. Call Him God, Allah or what ever. But onw thing is sure he is Almighty and All wise.