The proven Zacks Rank system focuses on earnings estimates and estimate revisions to find winning stocks. Nevertheless, we know that our readers all have their own perspectives, so we are always looking at the latest trends in value, growth, and momentum to find strong picks.Of these, perhaps no stock market trend is more popular than value investing, which is a strategy that has proven to be successful in all sorts of market environments. Value investors use a variety of methods, including tried-and-true valuation metrics, to find these stocks.Zacks has developed the innovative Style Scores system to highlight stocks with specific traits. For example, value investors will be interested in stocks with great grades in the "Value" category. When paired with a high Zacks Rank, "A" grades in the Value category are among the strongest value stocks on the market today.One company to watch right now is Group 1 Automotive (GPI). GPI is currently sporting a Zacks Rank of #1 (Strong Buy) and an A for Value. The stock is trading with P/E ratio of 6.31 right now. For comparison, its industry sports an average P/E of 7.27. Over the last 12 months, GPI's Forward P/E has been as high as 9.62 and as low as 5.67, with a median of 7.39.We should also highlight that GPI has a P/B ratio of 1.89. The P/B is a method of comparing a stock's market value to its book value, which is defined as total assets minus total liabilities. This company's current P/B looks solid when compared to its industry's average P/B of 2.19. Within the past 52 weeks, GPI's P/B has been as high as 2.19 and as low as 1.51, with a median of 1.80.Value investors also frequently use the P/S ratio. This metric is found by dividing a stock's price with the company's revenue. Some people prefer this metric because sales are harder to manipulate on an income statement. This means it could be a truer performance indicator. GPI has a P/S ratio of 0.28. This compares to its industry's average P/S of 0.46.Finally, investors should note that GPI has a P/CF ratio of 5.59. This metric focuses on a firm's operating cash flow and is often used to find stocks that are undervalued based on the strength of their cash outlook. GPI's current P/CF looks attractive when compared to its industry's average P/CF of 10.78. Over the past year, GPI's P/CF has been as high as 8.49 and as low as 4.68, with a median of 6.55.These figures are just a handful of the metrics value investors tend to look at, but they help show that Group 1 Automotive is likely being undervalued right now. Considering this, as well as the strength of its earnings outlook, GPI feels like a great value stock at the moment. More Stock News: This Is Bigger than the iPhone! It could become the mother of all technological revolutions. Apple sold a mere 1 billion iPhones in 10 years but a new breakthrough is expected to generate more than 77 billion devices by 2025, creating a $1.3 trillion market. Zacks has just released a Special Report that spotlights this fast-emerging phenomenon and 4 tickers for taking advantage of it. If you don't buy now, you may kick yourself in 2022.Click here for the 4 trades >>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 Group 1 Automotive, Inc. (GPI): Free Stock Analysis Report To read this article on Zacks.com click here.