Probably one of the most common questions on many investors' minds right now is whether they should buy stocks today or wait. After all, the S&P 500 is down 21% from recent highs. Is this a buying opportunity, or is there more pain to come?

More specifically, investors are likely wondering if the market has officially bottomed out or not. To this end, though the S&P 500 was down more than 30% at one point in March, it has rebounded 20% since then.

What should investors do? Buy the dip now or wait for a possible bigger drop?

These are good questions and fair concerns. To find answers, why not turn to one of the greatest investors of all time, Warren Buffett? The Oracle of Omaha has not only survived many downturns, but he's doubled the market's average annual compounded rate of return since 1965.

Here's Buffett's advice for a stock market crash.

A bear wearing a face mask and a chart showing stocks falling

Image source: Getty Images.

Don't try to time the bottom

While Buffett may be nicknamed the Oracle of Omaha, he's always been quick to admit that timing the market is a fool's errand, even for himself.

"I make no attempt to forecast the market -- my efforts are devoted to finding undervalued securities," the Berkshire Hathaway (BRK.A -0.36%) (BRK.B 0.11%) chairman and CEO has said.

Buffett has taken this stance even further, implying in Berkshire's 1992 shareholder letter that near-term market forecasts can be "poison" for investors. 

We've long felt that the only value of stock forecasters is to make fortune tellers look good. Even now, Charlie [Munger] and I continue to believe that short-term market forecasts are poison and should be kept locked up in a safe place, away from children and also from grown-ups who behave in the market like children.

In other words, instead of focusing his energy on timing the market, Buffett devotes his efforts to finding great businesses at good prices. "If we think a business is attractive, it would be very foolish for us to not take action on that because we thought something about what the market was going to do," Buffet said during the company's 1994 shareholder meeting."If you're right about the businesses, you'll end up doing fine." 

It's Buffett's skill at finding undervalued high-quality businesses that has earned him the nickname Oracle of Omaha -- not his ability to time the market. Further, his decision to avoid timing the market has likely aided his stock-picking prowess.

Don't waste a good buying opportunity

One of the biggest problems with investors making market timing a key part of their investment strategy is that it can result in missing out on opportunities to buy stocks at lower prices while they are busy trying to predict a bottom of a market sell-off. Since predicting the bottom of a downturn is so difficult (if not impossible) the best way for investors to take advantage of these opportunities is to simply be a net buyer of stocks over time, particularly when stocks of quality companies go down in price.

Warren Buffett at a Berkshire Hathaway shareholder meeting.

Warren Buffett. Image source: The Motley Fool.

When asked in February about the market declining amid coronavirus concerns, Buffett said, "That's good for us actually. We're a net buyer of stocks over time." He went on to compare it to how consumers view prices of food. "Just like being a net buyer of food, I expect to buy food the rest of my life -- and I hope that food goes down in price tomorrow." He concluded: "When stocks go down, we're going to be buying on balance." There was no mention of waiting to buy after the market has fallen to a certain level.

While Buffett doesn't advise investors to try to predict a bottom before they start buying stocks, he does clearly assert that downturns are opportunities to buy. "A market downturn doesn't bother us. It is an opportunity to increase our ownership of great companies with great management at good prices," Buffett has said. 

Of course, another sage word of advice for times like these is one of Buffett's most famous lines of all: "Be fearful when others are greedy and greedy when others are fearful."

So, if you're an investor in individual stocks, spend your time looking for undervalued companies to buy instead of trying to time the market. If you buy index funds, continue dollar-cost averaging and consider buying a bit more aggressively as the market falls.

Get in the game and stay in it

Probably the biggest takeaway from Buffett's discussions on market crashes and market timing is simply this: Be a net buyer of stocks and stay invested for the long haul.

Consider Buffett's observation on investing in Berkshire's 2012 shareholder letter:

Since the basic game is so favorable, Charlie and I believe it's a terrible mistake to try to dance in and out of it based upon the turn of tarot cards, the predictions of 'experts,' or the ebb and flow of business activity. The risks of being out of the game are huge compared to the risks of being in it.

Investors risk doing greater damage than good to their portfolio by timing the market. Instead, follow Buffett's tried and true method of buying, holding, and adding to stocks over time.

So, should investors buy stocks now or wait?

With the S&P 500 down 21% from recent highs, there are likely more good deals in the stock market today than there were in mid-February. Investors, therefore, should keep buying, whether this proves to be the bottom or not. Over the long haul, investing during downturns like this can provide a nice boost to investment returns.