This morning, I suddenly realised how to increase the tension in a story. It came to me while I was reading a story that worked well from the tension point of view. As soon as possible, I wrote it down. It doesn't matter that it's not perfect. I can work on the finer points later. The important thing is that it's written down. Had I been out of the house, I would have scribbled a note or used my dictaphone. It involved a character not being where she was expected and then reappearing in an odd place. Doesn't sound much, but makes all the difference in the story.
In fact, I've just given myself another idea, so I'll end there.