Building a successful investment portfolio takes skill and hard work, no matter if you're a growth, value, income, or momentum-focused investor.How do you find the right combination of stocks that will generate returns that could fund your retirement, or your kids' college tuition, or your short- and long-term savings goals?Enter the Zacks Rank.What is the Zacks Rank?The Zacks Rank, which is a unique, proprietary stock-rating model, employs earnings estimate revisions, or changes to a company's earnings expectations, that makes building a winning portfolio easier.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.These four factors are assigned a raw score that's recalculated every night, which is then compiled into the ranking system. Stocks are classified into five groups using this data, 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.Institutional investors are the professionals who manage the trillions of dollars invested in mutual funds, investment banks, and hedge funds. Studies have shown that these investors can and do move the market due to the large amounts of money they invest with. Because of this, the market tends to move in the same direction as institutional investors.In order to figure out the fair value of a company and its shares, these investors will build valuation models focused on earnings and earnings expectations. Because if you raise estimates for the bottom line, it creates a higher fair value for 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.Since it can often take weeks, if not months, for an institutional investor to build a position (given their size), retail investors who get in at the first sign of upward earnings estimate 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 Ovintiv (OVV), which was added to the Zacks Rank #1 list on July 7, 2021.Ovintiv Inc. is an independent energy producer, which explores and churns out oil and natural gas from diverse assets located in the United States and Canada. Previously known as Encana, the company rebranded and shifted its corporate domicile from Calgary, Canada to Denver, U.S. Four analysts revised their earnings estimate higher in the last 60 days for fiscal 2021, while the Zacks Consensus Estimate has increased $1.42 to $4.88 per share. OVV also boasts an average earnings surprise of 24.3%.Earnings are forecasted to see growth of 1294.3% for the current fiscal year, and sales are expected to increase 25.7%.OVV has been moving higher over the past four weeks as well, up 5.9% compared to the S&P 500's gain of 2.6%.Bottom LineWith a #1 (Strong Buy) ranking, positive trend in earnings estimate revisions, and strong market momentum, Ovintiv 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 >> Breakout Biotech Stocks with Triple-Digit Profit Potential The biotech sector is projected to surge beyond $2.4 trillion by 2028 as scientists develop treatments for thousands of diseases. They’re also finding ways to edit the human genome to literally erase our vulnerability to these diseases. Zacks has just released Century of Biology: 7 Biotech Stocks to Buy Right Now to help investors profit from 7 stocks poised for outperformance. Recommendations from previous editions of this report have produced gains of +205%, +258% and +477%. The stocks in this report could perform even better.See these 7 breakthrough stocks now>>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 Ovintiv Inc. (OVV): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research