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?A unique, proprietary stock-rating model, the Zacks Rank uses earnings estimate revisions, or changes to a company's earnings expectations, to ...