The Dow Jones Industrials (^DJI -0.11%) finished off the first quarter in record fashion on Thursday, closing at another all-time high. With greedy investors coming off the sidelines and cautious investors wondering if the good times are about to end, no one's sure what's coming next.

To get some insight on that question, here are five keys to understanding the Dow's record-setting quarter.

1. The Dow's gains were historically strong.
The stock market's rise on Thursday capped a run that has pushed the average up by 1,475 points so far this year. That translates to an 11% gain, which gave the Dow its biggest increase for a first quarter in 15 years. In raw point terms, it was the biggest quarterly gain ever for the average, although there have been other quarters in which the percentage change was greater.

2. The Dow's best performers were turnaround-driven.
Topping the list of Dow winners for the quarter was Hewlett-Packard (HPQ 1.55%), which soared 68%. After a horrendous 2012 in which the stock lost 43% of its value, HP has finally come up with a turnaround strategy that investors seem to believe in. Weakness in the PC industry will continue to weigh on HP for a long time even if the company does manage to make a successful transition to other more lucrative lines of business, such as cloud-computing solutions and broader-based IT consulting. Nevertheless, HP achieved an essential milestone by getting rid of investors' pessimism.

Meanwhile, Travelers (TRV -0.41%) gained a less impressive but still substantial 18%. Even in the wake of huge losses from Hurricane Sandy, Travelers has been able to increase premiums, putting itself in a position to boost long-term profits.

3. The Dow's worst performers point to a global slowdown.
Even in a record-breaking quarter, a couple of laggards didn't manage to post gains. Caterpillar (CAT 0.07%) and Alcoa (AA) were the Dow's only losers this quarter, and although their declines were relatively minor at just 2% and 3% respectively, their experience points to a general concern affecting the entire global economy.

For years, rising stock markets in emerging markets have hinged on the growth in overall economic activity, and with their pure-industrial roots, both Caterpillar and Alcoa have relied on good global economic health to support their businesses. As well as things are looking in the U.S. right now, the poor performance of these two stocks remind us that around the world, things are looking a lot different, and future crises could be right around the corner from unexpected locations across the globe.

4. Dividends continue to drive the Dow.
In a low-interest-rate environment, investors continue to look for income from their stock investments, and the Dow continues to pay rising dividends. The Dow's overall dividend yield has fallen slightly since this time last year, but with the Dow up more than 10% since March 2012, even a slight drop in yield doesn't come close to offsetting the increase in total payouts among Dow-component companies.

Some of the increases this quarter have continued to be strong. Both Coca-Cola and HP managed to push dividends higher by 10%, keeping pace with the Dow's overall rise. With many more companies expected to boost payouts in the near future, dividends will continue to be a driving force for further Dow advances.

5. Valuations on the Dow are reasonable.
Given the gains in the Dow, it's natural to be concerned about valuation. But with strong earnings performance, market multiples remain reasonable, with the Dow trading at about 16 times trailing earnings and less than 13 times forward earnings. Those figures are in line with the broader market as well.

The big question is whether earnings growth can continue. High profit margins have bolstered earnings in ways that some see as unsustainable, but without an imminent threat of reverting to more typical levels, a pullback doesn't necessarily have to come soon.

Enjoy the record!
The four-year bull market has made many investors happy, and with the Dow's record-setting quarter, the good times are clearly here. How long they'll stay is uncertain, but making the most of them while they last will be an essential part of a successful investing strategy.