When I'm perusing the menu of my favorite Chinese restaurant, I usually end up back at my regular: General Tso's chicken. It's familiar, it's safe, and I know I'll like it.

But sometimes I'm feeling a little adventurous, and I'll want to dabble: Time for a pupu platter.

Many of us come to a similar crossroads in investing, too. We're told that we should buy shares in companies we're familiar with . but then again, maybe a portfolio should have a "sampler" effect, with a little bit of everything, in a diversified portfolio. A pupu portfolio. Such diversity can protect us from the market's vagaries, after all.

We're proponents of sticking with companies you're familiar with and understand, especially for beginning investors. It's a key lesson from Peter Lynch's classic One Up on Wall Street. But that doesn't mean you can't break out of a self-imposed mold. Make sure that by sticking to what you know, you aren't closing your mind to the benefits of a diverse portfolio.

A diverse grab bag
I admit, I'm a big fan of buying what I know. I own shares of Starbucks (NASDAQ:SBUX), which I have followed closely for several years now -- not to mention my daily visits to the local store. I once held (and unfortunately, long since sold) shares of Amazon.com (NASDAQ:AMZN), a retailer whose virtual mall I have frequented since its launch.

In the two-plus years I've worked at the Fool, I've written primarily about the things that interest me personally -- trends in hot consumer brands, technology, and media. Netflix (NASDAQ:NFLX) is one of the companies I like to watch. It turned an entire industry on its ear by doing what many people thought impossible: offering DVD rentals over the Internet, to be delivered by old-fashioned U.S. mail.

But many of the best-known, hottest consumer brands carry the highest price tags attached to their stocks -- and a whole lot of buzz-driven volatility. Some of you may remember when Netflix's stock took quite a hit, based on competition from Blockbuster (NYSE:BBI) and the threat of Amazon entering the online DVD rental business. It has since recovered, of course, given Amazon's reticence at entering the U.S. market and Wal-Mart's (NYSE:WMT) decision to drop out of the DVD rental race.

So where will we find diversity in our portfolios to offset the inevitable market ups and downs that accompany hot stocks? Find the business models we already know in industries we don't follow.

For example, what do Corporate Executive Board (NASDAQ:EXBD) and Netflix have in common? The quick answer: Not much. Corporate Executive Board is as obscure as Netflix is mainstream. Its focus on corporate information is hardly common knowledge to the average Joe, while Netflix's red mailers are part of the decor in many a household. There's a huge difference between corporate information services and renting Old School to people over the Internet, right? Well, yes and no.

Different strokes; investors stoked
Netflix, which David Gardner has recommended for Motley Fool Stock Advisor twice, is a company that delivers a popular, subscription-based service. Its most recent subscriber number had it ahead of its earlier prognostications for the year, at 4 million. And there's surprisingly low subscriber churn. Surely it's helped by innovative programs like its Netflix Friends feature, which allows users to create a rather viral network of friends to share movie recommendations, reviews, and ratings. Netflix Friends creates a community draw -- and more reasons to stick around).

Despite a high-profile price war, last quarter Netflix was profitable, managing a 23% year-over-year increase in sales. Meanwhile, despite its highly competitive category, it sports $182 million in cash and no debt.

Corporate Executive Board doesn't share the pop-culture spotlight that Netflix enjoys. But it shares a few resemblances with Netflix, most notably its subscription-based model and strong momentum toward subscriber retention.

When Tom Gardner singled out Corporate Executive Board for Motley Fool Stock Advisor in August 2002, he recognized a real strength -- a subscription-based model that fostered subscriber loyalty (in 2004, its client renewal rate was 91%). Corporate Executive Board sells collaborative business research to its member companies. At the moment, it boasts 2,400 large corporate members, including more than 80% of the Fortune 500. Each pays a large yearly fee to join the network, where they share ideas, problems, and solutions. Corporate Executive Board, in turn, turns this community-created data into analytical reports.

That approach has helped the company achieve steady growth and high renewal rates. Meanwhile, as you can imagine, capital expenditures are low. Corporate Executive Board recently reported several exciting quarters, with sales growth rates at 30%. It also has a strong balance sheet, with $336 million in cash and no debt.

So there you have it -- two companies with similar strengths, although at first glance, you'd never think to compare.

Buy what you know . and what you get to know
Netflix and Corporate Executive Board are prime examples of stocks that certainly don't seem to have similarities, but both have made great additions to investors' portfolios. Indeed, Corporate Executive Board shares have increased 200% since Tom recommended the company in 2002. The point is, even if you subscribe to the tenet of buying what you know, you have a better shot at having a more diverse portfolio if you get to know more stocks.

Not sure how to start? A service like Motley Fool Stock Advisor can help you diversify your investment portfolio by finding opportunities similar to the stocks you already know, in places you might not have previously thought to look. Click here for a 30-day free trial to Motley Fool Stock Advisor, and get access to more than 60 formal recommendations Tom and David have made since the newsletter's inception.

So whether you go for General Tso's chicken or branch out into the pupu platter, buy what you know, but don't box yourself in.

Netflix , Corporate Executive Board, and Amazon.com are Motley Fool Stock Advisor picks.

Alyce Lomax owns shares of Starbucks, but of none of the other companies mentioned; her Netflix queue has a whopping 200 movies in it, so she's not going anywhere. The Fool has a disclosure policy.