We all know what we're supposed to do during a bear market. But until you've actually been in that situation, you don't really know what it takes to pull the trigger and put real money at risk -- especially at times when every instinct you have is telling you that you're throwing that money away.

Now, battle-tested investors have a full-fledged big bad bear under their belts. We all went through last year's financial crisis, two big dips in the stock market in November and March, and the incredible rally from those lows. We've seen threats from both deflationary and inflationary pressures. And although plenty of challenges still face the economy, such as an escalating loss of confidence in the dollar, few people are still worried about a complete systemic breakdown of the entire financial system.

As an investor, you'll face moments of panic and euphoria countless times in the future. Ideally, you'll use your experiences over the past year as a learning tool for how to handle your investments the next time around. Here are three things you can take from the financial crisis and the ensuing recovery.

1. You won't know the bottom when it comes.
One of the first things you learn in investing is to buy low and sell high. However, that maxim neglects to mention that during bear markets, there's always a perfectly plausible reason why stocks are low -- and why you shouldn't buy them. Last November, executives from Ford (NYSE:F), GM, and Chrysler were asking the government for bailout money, while lawmakers and economists were still trying to figure out exactly what the recently approved TARP program was supposed to do.

Meanwhile, in March, Warren Buffett had announced that the economy had "fallen off a cliff;" at the same time, the World Bank was predicting a global contraction. Bank of America (NYSE:BAC) had to resort to issuing debt backed by the FDIC to raise capital.

At either of those points, it seemed downright likely that stocks would keep falling. But each of those times turned out to be great buying opportunities. There was simply no way you could have known that at the time.

The key, therefore, is not to try to guess the exact bottom. Instead, if you commit your capital gradually over time, you'll get some of your money in near the bottom. And while you won't get the absolute best returns possible, you'll still do pretty well.

2. Any stocks can become good values.
Over the past six months, companies like Citigroup (NYSE:C), MGM Mirage (NYSE:MGM), and AIG (NYSE:AIG) have taken a lot of heat for benefiting from the "junk rally" in stocks. Yet while it's interesting that speculative stocks have done so well, it shouldn't be surprising.

In March, many risky stocks were priced for absolute failure. With the collapse of Lehman Brothers and the impending bankruptcies of GM and Chrysler, it seemed that no company was completely safe from utter collapse. Investors bid down shares accordingly.

Yet as it turned out, those moves were a complete overreaction. Once it became clear that those companies wouldn't immediately shut down despite the financial straits they were in, their stocks took off. Most of them still trade at levels far below where they were two or three years ago. But despite the risk involved, they were priced so low at the time that investors comfortable with that risk stood to make big gains -- and did.

Over the long run, good companies will outperform bad ones. But in a six-month span, anything can happen. Opportunities can appear anywhere, so be ready for them when they do.

3. Don't count on getting in later.
As the rally continued, many investors waited for stocks to revisit their lows or at least go through a moderate correction. But many big gainers, such as Apple (NASDAQ:AAPL) and Baidu (NASDAQ:BIDU), advanced for months without seeing much more than a rare 10% dip along the way.

If you like a stock at a certain price, don't count on getting a better one. That doesn't mean you should ignore valuation entirely -- but if a stock meets your criteria for a bargain, then getting greedy could cost you a lot more than the dollar or two you save waiting for a pullback.

Remember the crisis
What you've learned in the heat of the moment during the financial crisis can guide you for the rest of your investing career. Even if you didn't meet your own expectations during this crisis, you'll do a better job of capitalizing on your next opportunity if you can take those lessons to heart.

The market meltdown has taught investors many lessons about stocks, the economy, and more. Read our retrospective on the financial crisis and make sure you've learned everything you can from it.

Fool contributor Dan Caplinger has learned a lot of lessons in the past year. He doesn't own shares of the companies mentioned in this article. Baidu is a Motley Fool Rule Breakers recommendation. Apple is a Stock Advisor selection. Try any of our Foolish newsletter services free for 30 days. The Fool's disclosure policy is a great teacher.