Yeah, my writing improved tremendously once I realized that you shouldn't hide anything from the reader. If the characters know something, then it should be told to the reader immediately. Trying to keep readers "guessing" doesn't heighten the tension or create more suspense (which is what writers usually think). Instead, it just ticks readers off when something is finally revealed.

Now, if the characters DON'T know a piece of information, that's a different story. And if you can work it so that you've given the reader the information and they don't realize it, that's even better.