Keeping your investments simple makes your life a little easier. But with just a bit of extra effort, you can earn better returns -- which will make your life a lot easier.

In putting together a winning portfolio, the right mix of different types of investments makes all the difference. By tailoring an asset allocation strategy to your particular financial situation, you can ensure that you're taking on the optimal level of risk, while staying on track to meet your long-term goals.

Asset allocation and you
Exactly how you implement that asset allocation strategy can make a big difference. In this month's brand-new issue of Rule Your Retirement -- available here on the Fool website this afternoon at 4 p.m. ET -- Foolish retirement expert Robert Brokamp takes a closer look at the topsy-turvy turns of the financial markets during 2008 and 2009. Over that time frame, different asset classes have moved in and out of favor so quickly that there's simply no way anyone could hope to keep up.

To help you take action, Robert has long provided model portfolios for his Rule Your Retirement subscribers. In the new issue, he talks about some changes he recently made to those models. Not only has he made them somewhat more aggressive, but he's also gone beyond simple core holdings, adding some niche investments that can spice up your returns.

Finding value
Perhaps the most important addition to the model portfolios appears in their explicit allocations to value-based investments. A number of academic studies have discovered that value stocks have outperformed growth stocks over the long haul. Moreover, that isn't just true for large-cap value stocks -- among small caps, value stocks have also shown a pronounced bias toward better performance.

Of course, most all-purpose funds will already include some value stocks. For instance, Vanguard includes stocks such as ExxonMobil (NYSE:XOM), Verizon (NYSE:VZ), and Merck (NYSE:MRK) when picking holdings for its value-stock ETF. Any broad index fund, and many actively managed funds, will own a healthy portion of stocks like those.

But allocating a bit extra to value stocks takes advantage of that performance bump. It isn't that growth stocks like Cisco (NASDAQ:CSCO), Google (NASDAQ:GOOG), or Monsanto (NYSE:MON) are bad investments. During certain market periods, growth has done much better than value. For a truly long-range plan, however, you're better off having more of your money in value stocks.

Running the numbers
To show what a difference a more detailed asset allocation plan can make, Robert compared the returns of a basic core portfolio approach against the returns using a wider variety of niche investments. The results were astounding: On a $100,000 investment made 10 years ago at the height of the 1990s bull market, the expanded portfolio produced nearly $15,000 more in profits than the core portfolio did.

On the other hand, these returns don't come for free. The price you pay for higher performance is somewhat greater volatility. Especially among some of the more exotic niche asset classes -- areas such as emerging-market stocks and micro-cap companies, for instance -- you'll see a lot more ups and downs in your portfolio than you'd typically experience with blue chips. For instance, Brazilian oil giant Petrobras (NYSE:PBR) has risen an average of 48% per year in the past five years -- but during 2008, the stock dropped almost 80% from the end of June to November's lows. As long as you have a long time horizon, however, the bumps should smooth out, leaving you with better results in the end.

Learn more
For investors looking for guidance on the best asset allocation strategy, Robert's three model portfolios are tailored with specific allocation percentages appropriate for investors at different stages of their careers. They're definitely worth a look, along with the more in-depth discussion Robert includes about the basics of his investment strategy.

If you're curious to see more, it's easy to become a subscriber to Rule Your Retirement. In fact, we'd love to offer you a free look at the new issue, as well as everything else our retirement newsletter service has to offer. Just click here to claim your free trial today. It could prove to be your start on the road to a wealthier retirement.

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Fool contributor Dan Caplinger loves his niche holdings. He doesn't own shares of the companies mentioned. Google is a Motley Fool Rule Breakers pick. Petrobras is a Motley Fool Income Investor selection. Try any of our Foolish newsletters today, free for 30 days. The Fool's disclosure policy always goes a step further.