If you want to be a wildly successful investor, you'll need to invest in some wildly successful companies (or mutual funds, or apartment buildings, etc.). But zeroing in on the most promising companies is easier said than done. One way I like to invest is to build a list of wonderful companies and then watch for their stocks to fall to compelling levels.

To help you determine whether the company you're looking at is a first-class operation you'd be proud to have in your portfolio, here are five hallmarks of great companies:

1. Powerful brands
Think of well-known brand names in the United States or, better yet, around the world. PepsiCo (NYSE:PEP), Microsoft (NASDAQ:MSFT), and IBM (NYSE:IBM) are all among the top 100 brands in the world, as ranked by Interbrand. This kind of popular recognition can give these companies a leg up in their industries.

2. Significant products or services
Look for a company that's selling its customers something they really need or really want. Pharmaceutical companies such as Merck (NYSE:MRK), for example, manufacture products that people will buy whether they're flush with funds or strapped for cash. (If you're losing bone mass, for example, you're probably not going to forego taking your Fosamax in order to save a few bucks.) Firms such as the aforementioned PepsiCo and Anheuser-Busch (NYSE:BUD) offer consumers products they love and purchase over and over again.

3. Consistent, reliable earnings and sales growth -- and robust margins
Great companies grow steadily and find ways to get more and more of their revenue to the bottom line.

4. Strong leadership
This is in many ways a qualitative factor, but that doesn't mean you can't ferret out some useful impressions and information. Learn some tricks in these articles: "Identifying Effective Management" and "Investigative Investing."

5. A lasting competitive advantage
Think of Stock Advisor recommendation eBay (NASDAQ:EBAY), for example. Any company that wanted to build a massive online marketplace would have trouble competing. eBay has had too much of a head start, and its networking effects would make it very difficult for a competitor to steal market share.

And then there's price .
Once you've identified a great company, you may be tempted to rush out and buy shares at any price. Don't. High-quality companies often trade at premium prices, and paying too much for a stock will hurt your returns. But if you're patient, you'll likely find one or more on sale every now then.

Great companies at good prices. That's a recipe that can help you beat the market for decades, and it happens to be a good way to summarize the strategies that Fool co-founders David and Tom Gardner employ in their Motley Fool Stock Advisor investing service. And they're having some success. To date, their picks are beating the S&P 500 by nearly 40 percentage points. If you'd like to see what great companies they're recommending today -- a brand-new issue of Stock Advisor releases at 12 noon ET -- click here to preview the service with no obligation to subscribe.

Longtime Fool contributor Selena Maranjian owns shares of PepsiCo, Microsoft, and eBay. For more about Selena, view her bio and her profile. Microsoft and Anheuser-Busch are Motley Fool Inside Value recommendations. Merck is a former Income Investor pick. The Motley Fool isFools writing for Fools.