I'm so glad you asked that because dreams, first of all, are a way that the brain recharges. The brain is like a battery, it MUST recharge. If you are sleep deprived, the brain will eventually just go into REM sleep (dream sleep). The brain does 90 minute cycles all night. You won't remember a dream unless you wake up near or when you've had it. Okay, that said...
Now, I've had dreams ONLY THREE that were about future events in my life. I was in denial about it but now, well, what can I say? I dreamed about things that happened years later. I watched it unfold and was IN denial. I could NOT believe it. I think it's GOD's way of softening the blow. One dream has not come true yet and I hope it does not. It was NOT pretty. It was quite serious.
Okay, the dreams that are "prophetic" you will know because they stay with you and you think about them. They just seem to come to mind without you calling them. I believe these kinds of dreams are not plentiful, they're more rare but you, yourself will know.