When I was learning to write, someone made a comment about tension in a story. Well, I recognized tension when I saw it, but wasn't really sure how to go about creating it. I had one clue, though, from my husband. When he tells a story, he always gets to the good part, the part where you just have to know more and he stops. So you either have to ask a question and look a little bit dumb, or be patient and wait. I hate waiting.
So I went looking through all the writing books for an explanation of tension. The best I found was in Sol Stein's book "Stein on Writing". He has two chapters, one dedicated to suspense, one dedicated to tension. That's where I learned that you really want to wind your character up to a pitch of emotion waiting for what everyone know is going to happen. The tension is all in the character's reaction to that awful event that is coming.
Does this mean I can do it every time? Not so easy, but I try.