Dividend investing is a tried-and-true strategy for generating strong, steady returns in economies both good and bad. But as corporate America's slew of dividend cuts and suspensions over the past few years has demonstrated, it's not enough simply to buy a high yield. You also need to make sure those payouts are sustainable.

Let's examine how Norfolk Southern (NYSE: NSC) stacks up. In this series, we consider four critical factors investors should examine in every dividend stock. We'll then tie it all together to look at whether Norfolk Southern is a dividend dynamo or a disaster in the making.

1. Yield
First and foremost, dividend investors like a large forward yield. But if a yield gets too high, it may reflect investors' doubts about the payout's sustainability. If investors had confidence in the stock, they'd be buying it, driving up the share price and shrinking the yield.

Norfolk Southern yields 2.7%, quite a bit higher than the S&P 500's 2%.

2. Payout ratio
The payout ratio might be the most important metric for judging dividend sustainability. It compares the amount of money a company paid out in dividends last year to the earnings it generated. A ratio that's too high -- say, greater than 80% of earnings -- indicates that the company may be stretching to make payouts it can't afford, even when its dividend yield doesn't seem particularly high.

Norfolk Southern has a modest payout ratio of 30%.

3. Balance sheet
The best dividend payers have the financial fortitude to fund growth and respond to whatever the economy and competitors throw at them. The interest coverage ratio indicates whether a company is having trouble meeting its interest payments -- any ratio less than 5 is a warning sign. Meanwhile, the debt-to-equity ratio is a good measure of a company's total debt burden.

Norfolk Southern has a moderate debt-to-equity ratio of 77% and an interest coverage rate of seven times.

4. Growth
A large dividend is nice; a large growing dividend is even better. To support a growing dividend, we also want to see earnings growth.

Over the past five years, Norfolk Southern's earnings per share have grown at an impressive average annual rate of 9%, while its dividend has grown at a 20% rate.

The Foolish bottom line
So, is Norfolk Southern a dividend dynamo? It could very well be. Although its above-average yield may not be massive, payouts have been rising sharply. With a reasonable debt load, a low payout ratio, and earnings growth, Norfolk should have the strength to continue growing those payouts in the coming years, if it decides to. If you're looking for some other great dividend stocks, I suggest you check out "Secure Your Future With 11 Rock-Solid Dividend Stocks," a special report from The Motley Fool about some serious dividend dynamos. I invite you to grab a free copy to discover everything you need to know about these 11 generous dividend payers -- simply click here.