August, in case you missed it, was a wild and wooly month for the stock market. Despite having recovered a bit, the Dow Jones Industrial Average (INDEX: ^DJI) is still down about 9% from where it was as recently as the third week of July.

That represents some recovery from the 15% swoon we saw between late July and mid-August, but for most of us, our portfolios are still down substantially from where they were in the spring. Looking at our portfolio after the market has taken a hit can often feel like a call to action -- I'm down, I need to do something! -- and generally the first thing we want to do is to try to figure out what's coming next.

There's just one problem with trying to foretell the future: You can't. While we can look at historical patterns and make some guesses, not even experts can reliably see beyond generalities -- and even those are often wrong.

But that doesn't mean there's nothing we can do.

The future remains cloudy, but some patterns are clear
You've surely heard the old joke about the economists who predicted 17 of the last three recessions. The truth is, it's hard to predict the economic future, even in broad terms -- and it's impossible to predict the timing of Mr. Market's mood swings.

But it's not impossible to predict that Mr. Market will have big swings -- in fact, we can count on it. My Foolish colleague retirement guru Robert Brokamp recently ran some numbers on drops in the Dow. It turns out that a 15% drop like the one we just had is a pretty common event -- since 1900, 15% drops have happened about once every two years, on average.

We can't predict the timing, but we can predict that they'll happen. And more to the point, we can be ready.

The next drop is coming. Are you ready?
Are there stocks you've been following? Are there companies you'd like to own or positions you'd like to add to if only the price were a little lower? Thinking about these questions now is key to being ready to use a gut-churning market drop to your long-term advantage.

Like a lot of savvy Fools, I had a big buy list ready to go when the market was gyrating in early 2009, and when it seemed to be bottoming, I bought several of my favorite companies. Some of the stocks I bought then, like well-managed liquor giant Diageo (NYSE: DEO), will probably be in my portfolio for many years -- and nearly everything I bought went up big in the months that followed.

I didn't make as many buys during this past drop, even though I had some cash to invest -- mostly because I was on vacation during the worst of it -- but I did log in from the beach and add to a couple of big positions at discount prices. General Motors (NYSE: GM) in particular seemed like a screaming buy to me. While there's lingering concern about the company's pension liability and the government's continued stake, I'm seeing lots of signs that an impressive turnaround is brewing, and I think many are still missing that story.

But even if you don't have a watchlist, there are some general principles you can fall back on during a market drop -- or even right now.

An all-purpose approach to the near future
My aforementioned colleague Robert Brokamp has a great article in the new issue of the Fool's Rule Your Retirement newsletter on how to protect -- and enhance -- your portfolio during periods when the market is down.

Robert offers several great strategies, most of which are good ideas anytime -- especially right now, while the market's still down. For instance, blue-chip dividend stocks like well-diversified pharma giant Abbott Labs (NYSE: ABT), globally growing soda-and-snack king PepsiCo (NYSE: PEP), and international tobacco colossus Philip Morris International (NYSE: PM) are in some ways the ultimate defensive stocks -- high-quality, recession-resistant businesses that pay you to hold them (via those dividends) even when Mr. Market's off his meds. Buying stocks like these when the market puts them on sale can bring your portfo lio benefits for decades.

Robert has several other great ideas, including a variation on market timing (yes, really) that may surprise you -- check out his article for the full scoop. Rule Your Retirement is a paid service, but you can get full access to Robert's article and all of the service's great content free of charge, with a no-obligation 30-day trial. Just click here to get started.

Fool contributor John Rosevear owns shares of Diageo, General Motors, and Abbott Labs, but he holds no other position in any company mentioned. You can follow his investing-related musings on Twitter at @jrosevear. The Motley Fool owns shares of Diageo, PepsiCo, Philip Morris International, and Abbott Labs. Motley Fool newsletter services have recommended buying shares of Diageo, Philip Morris International, PepsiCo, General Motors, and Abbott Labs, as well as creating a diagonal call position in PepsiCo. Try any of our Foolish newsletter services free for 30 days.