I have several reasons for believing in God, none of them decisive perhaps, but taken together I find them pretty compelling. Here are at least some of them:
I have heard enough accounts of miracles, divine communications, and such (like a few that have been reported in this thread), some at least of them from reliable enough sources, to make me more inclined to believe that at least some of them were actual glimpses of God in action than that they were all hallucinations, hoaxes, coincidences, or other natural phenomena.
There have been times when I have prayed and felt like I was getting through to Somebody, and that my prayers were being heard and answered or at least considered. (There have also been plenty of times when I have prayed but felt like I was praying to a brick wall.) And there has been at least one instance when either God spoke to me directly or else my mind tricked me into thinking he did. (Or both: maybe that’s how God spoke.)
The universe: it’s so intricate and beautiful, I find it easier to believe that it was designed by a Creator than that it Just Randomly Happened.
The Bible, especially the Gospel accounts of Jesus: when I read the accounts of what he said and did, there’s something very compelling there that demands to be taken seriously.
Other believers. When I consider the very wisest and goodest people I know, both in person and by reputation (writers, historical figures, etc.), the vast majority of them are believers, particularly Christians. Sure, there are a lot of nit-wit religious people, and a lot of smart, admirable atheists, but in my experience the very upper end of the scale is mostly believers. I see this as, at least, conclusive proof that it is not foolish to believe.
I believe the universe has a moral dimension. I believe that certain actions are evil, and that saying so is saying something objective beyond just “I don’t like them.” Likewise, some actions are good. Since I believe in good and evil, I have to believe in something beyond just the natural, physical world.