I've found that if I want to look foolish, I predict short-term movements in the stock market. Or long-term movements.
Still, if you are like me and the real reason you're buying stocks today is the anticipation of having retirement money in a decade or so, I do have some advice. You know that stock that you were, about a month or two ago, wistfully thinking it would be nice to have bought a year before? Buy it this week. I'm not sure if it will go down even more or will bottom out this week. All I do know is that it is selling for less than it was when you wished you owned it. And that might just qualify as a bargain.