No one has been able to time the market consistently (profitably). A look at this chart should show you why it's so difficult. Talk about volatility!
Very few people are in the black right now (on a Year-To-Date basis) which is why it's very important to follow some Hitchhiker's Guide To The Galaxy Advice: Don't Panic.
That's actually good advice for such volatile markets if you're like most people - a long term investor. Unless you're a day trader, or really know what you're doing, volatile markets can often present the best buying opportunities. Remember - be careful, do your homework, and if everything still makes sense - be patient and don't panic.
Addendum: I added Berkshire to the comparison chart because of all the talk on Warren Buffett. Don't interpret it as a buy recommendation or anything else - it's just an interesting point of reference for the chart.
Addendum 2: Reports say the markets are going to open sharply lower today, after yesterday's extremely volatile trading. I try not to get caught up in the day to day news of the market except when volatility presents buying opportunities.