Whether you're a growth, value, income, or momentum-focused investor, building a successful investment portfolio takes skill, research, and a little bit of luck.But how do you find the right combination of stocks? Funding your retirement, your kids' college tuition, or your short- and long-term savings goals certainly requires significant returns.Enter the Zacks Rank.What is the Zacks Rank?The Zacks Rank is a unique, proprietary stock-rating model that utilizes earnings estimate revisions to help investors build a winning portfolio.There are four main factors behind the Zacks Rank: Agreement, Magnitude, Upside, and Surprise.Agreement is the extent to which all brokerage analysts are revising their earnings estimates in the same direction. The greater the percentage of analysts revising their estimates higher, the better chance the stock will outperform.Magnitude is the size of the recent change in the consensus estimate for the current and next fiscal years.Upside is the difference between the most accurate estimate, which is calculated by Zacks, and the consensus estimate.Surprise is made up of a company's last few quarters' earnings per share surprises; companies with a positive earnings surprise are more likely to beat expectations in the future.Each one of these factors is given a raw score that's recalculated every night, and then compiled into the Zacks Rank. Using this data, stocks are classified into five groups, ranging from "Strong Buy" to "Strong Sell."The Power of Institutional InvestorsThe Zacks Rank also allows individual investors, or retail investors, to benefit from the power of institutional investors.These professionals manage the trillions of dollars invested in hedge funds, mutual funds, and investment banks, and studies have shown that they can and do move the market because of the large amounts of money they invest with. Thus, the market tends to move in the same direction as institutional investors.These investors are known for designing valuation models that focus on earnings and earnings expectations in order to figure out the fair value of a company and its shares. If earnings estimates are raised, it puts a higher value on a company.Institutional investors will use these changes to help in their decision-making, typically buying stocks with rising estimates and selling those with falling estimates. Higher earnings expectations can translate into a rise in stock price and bigger gains for the investor.Because it can take a long time for an institutional investor to build a position -- sometimes weeks, if not months -- retail investors who get in at the first sign of upward revisions have a distinct advantage over these larger investors, and can benefit from the expected institutional buying that will follow.Not only can the Zacks Rank help you take advantage of trends in earnings estimate revisions, but it can also provide a way to get into stocks that are highly sought after by professionals.How to Invest with the Zacks RankThe Zacks Rank is known for transforming investment portfolios. In fact, a portfolio of Zacks Rank #1 (Strong Buy) stocks has beaten the market in 26 of the last 32 years, with an average annual return of +25.41%.Moreover, stocks with a new #1 (Strong Buy) ranking have some of the biggest profit potential, while those that fell to a #4 (Sell) or #5 (Strong Sell) have some of the worst.Let's take a look at Lithia Motors (LAD), which was added to the Zacks Rank #1 list on July 17, 2021.Lithia Motors, Inc. is one of the leading automotive retailers of new and used vehicles, and related services in the United States. As of Dec 31, 2020, the company offered 33 vehicle brands across 209 stores in 22 states within the United States. The core brands offered by Lithia Motors include Chrysler, General Motors, Toyota, Subaru, Honda, Acura, Ford, BMW, MINI, Nissan and Hyundai.For fiscal 2021, two analysts revised their earnings estimate upwards in the last 60 days, and the Zacks Consensus Estimate has increased $1.22 to $24.23 per share. LAD boasts an average earnings surprise of 47.5%.Earnings are expected to grow 33.2% for the current fiscal year, while revenue is projected to increase 55%.Additionally, LAD has climbed higher over the past four weeks, gaining 8.9%. The S&P 500 is up 2.5% in comparison.Bottom LineWith a #1 (Strong Buy) ranking, positive trend in earnings estimate revisions, and strong market momentum, Lithia Motors should be on investors' shortlist.If you want even more information on the Zacks Ranks, or one of our many other investing strategies, check out the Zacks Education home page.Discover Today's Top StocksOur private Zacks #1 Rank List, based on our quantitative Zacks Rank stock-rating system, has more than doubled the S&P 500 since 1988. Applying the Zacks Rank in your own trading can boost your investing returns on your very next trade. See Today's Zacks #1 Rank List >> 5 Stocks Set to Double Each was hand-picked by a Zacks expert as the #1 favorite stock to gain +100% or more in 2021. Each comes from a different sector and has unique qualities and catalysts that could fuel exceptional growth. Most of the stocks in this report are flying under Wall Street radar, which provides a great opportunity to get in on the ground floor. Today, See These 5 Potential Home Runs >>Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report Lithia Motors, Inc. (LAD): Free Stock Analysis Report To read this article on Zacks.com click here.