For new and old investors, taking full advantage of the stock market and investing with confidence are common goals. Zacks Premium provides lots of different ways to do both.Featuring daily updates of the Zacks Rank and Zacks Industry Rank, full access to the Zacks #1 Rank List, Equity Research reports, and Premium stock screens, the research service can help you become a smarter, more self-assured investor.Zacks Premium also includes the Zacks Style Scores.What are the Zacks Style Scores?Developed alongside the Zacks Rank, the Zacks Style Scores are a group of complementary indicators that help investors pick stocks with the best chances of beating the market over the next 30 days.Each stock is assigned a rating of A, B, C, D, or F based on their value, growth, and momentum characteristics. Just like in school, an A is better than a B, a B is better than a C, and so on -- that means the better the score, the better chance the stock will outperform.The Style Scores are broken down into four categories:Value ScoreValue investors love finding good stocks at good prices, especially before the broader market catches on to a stock's true value. Utilizing ratios like P/E, PEG, Price/Sales, Price/Cash Flow, and many other multiples, the Value Style Score identifies the most attractive and most discounted stocks.Growth ScoreWhile good value is important, growth investors are more focused on a company's financial strength and health, and its future outlook. The Growth Style Score takes projected and historic earnings, sales, and cash flow into account to uncover stocks that will see long-term, sustainable growth.Momentum ScoreMomentum trading is all about taking advantage of upward or downward trends in a stock's price or earnings outlook, and these investors live by the saying "the trend is your friend." The Momentum Style Score can pinpoint good times to build a position in a stock, using factors like one-week price change and the monthly percentage change in earnings estimates.VGM ScoreWhat if you like to use all three types of investing? The VGM Score is a combination of all Style Scores, making it one of the most comprehensive indicators to use with the Zacks Rank. It rates each stock on their combined weighted styles, which helps narrow down the companies with the most attractive value, best growth forecast, and most promising momentum.How Style Scores Work with the Zacks RankA proprietary stock-rating model, the Zacks Rank utilizes the power of earnings estimate revisions, or changes to a company's earnings outlook, to help investors create a successful portfolio.It's highly successful, with #1 (Strong Buy) stocks producing an unmatched +25.41% average annual return since 1988. That's more than double the S&P 500. But because of the large number of stocks we rate, there are over 200 companies with a Strong Buy rank, plus another 600 with a #2 (Buy) rank, on any given day.But it can feel overwhelming to pick the right stocks for you and your investing goals with over 800 top-rated stocks to choose from.That's where the Style Scores come in.To have the best chance of big returns, you'll want to always consider stocks with a Zacks Rank #1 or #2 that also have Style Scores of A or B, which will give you the highest probability of success. If you're looking at stocks with a #3 (Hold) rank, it's important they have Scores of A or B as well to ensure as much upside potential as possible.The direction of a stock's earnings estimate revisions should always be a key factor when choosing which stocks to buy, since the Scores were created to work together with the Zacks Rank.Here's an example: a stock with a #4 (Sell) or #5 (Strong Sell) rating, even one with Style Scores of A and B, still has a downward-trending earnings outlook, and a bigger chance its share price will decrease too.Thus, the more stocks you own with a #1 or #2 Rank and Scores of A or B, the better.Stock to Watch: Petrobras (PBR)Headquartered in Rio de Janeiro, Petroleo Brasileiro S.A., or Petrobras S.A., is the largest integrated energy firm in Brazil and one of the largest in Latin America. The company’s activities include: exploration, exploitation and production of oil from reservoir wells, shale and other rocks, as well as refining, processing, trading and transportation of oil and oil products, natural gas and other fluid hydrocarbons, in addition to other energy-related activities. The company operates in five segments:PBR is a #3 (Hold) on the Zacks Rank, with a VGM Score of A.Additionally, the company could be a top pick for growth investors. PBR has a Growth Style Score of A, forecasting year-over-year earnings growth of 300% for the current fiscal year.For fiscal 2021, two analysts revised their earnings estimate upwards in the last 60 days, and the Zacks Consensus Estimate has increased $0.17 to $1.72 per share. PBR boasts an average earnings surprise of 308.9%.With a solid Zacks Rank and top-tier Growth and VGM Style Scores, PBR should be on investors' short list. Breakout Biotech Stocks with Triple-Digit Profit Potential The biotech sector is projected to surge beyond $775 billion by 2024 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. Our recent biotech recommendations have produced gains of +50%, +83% and +164% in as little as 2 months. 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 Petroleo Brasileiro S.A. Petrobras (PBR): Free Stock Analysis Report To read this article on Zacks.com click here.