How do you notice when you’re procrastinating?

I’m going to steal Anna’s idea and change it to the instrumental side of rationality. In Luke’s algorithm for beating procrastination, Step 1 is to Notice You Are Procrastinating. I’m not so sure this is easy. For me, the knowledge sort of fades in and out without being explicitly grabbed by my consciousness. If I actually held onto that fact, the moment that I was evading a task, and made it clear to myself that I was doing the sub-optimal, and the consequences involved, I think it would go a long way towards getting me to actually get things done.

What do you use to catch it? How do you notice you’re procrastinating? Leave your ideas below (one idea per comment), and upvote the comments that you either: (a) use; or (b) will now try using.