Here at Zacks, we focus on our proven ranking system, which places an emphasis on earnings estimates and estimate revisions, to find winning stocks. But we also understand that investors develop their own strategies, so we are constantly looking at the latest trends in value, growth, and momentum to find strong companies for our readers.Considering these trends, value investing is clearly one of the most preferred ways to find strong stocks in any type of market. Value investors use fundamental analysis and traditional valuation metrics to find stocks that they believe are being undervalued by the market at large.Luckily, Zacks has developed its own Style Scores system in an effort to find stocks with specific traits. Value investors will be interested in the system's "Value" category. Stocks with both "A" grades in the Value category and high Zacks Ranks are among the strongest value stocks on the market right now.One company to watch right now is Greif (GEF). GEF is currently sporting a Zacks Rank of #1 (Strong Buy), as well as an A grade for Value. The stock is trading with a P/E ratio of 10.16, which compares to its industry's average of 14.92. Over the past year, GEF's Forward P/E has been as high as 16.95 and as low as 9.69, with a median of 13.26.GEF is also sporting a PEG ratio of 1.02. This metric is used similarly to the famous P/E ratio, but the PEG ratio also takes into account the stock's expected earnings growth rate. GEF's PEG compares to its industry's average PEG of 1.65. GEF's PEG has been as high as 1.70 and as low as 0.97, with a median of 1.33, all within the past year.Value investors also use the P/S ratio. The P/S ratio is is calculated as price divided by sales. This is a prefered metric because revenue can't really be manipulated, so sales are often a truer performance indicator. GEF has a P/S ratio of 0.6. This compares to its industry's average P/S of 1.25.These figures are just a handful of the metrics value investors tend to look at, but they help show that Greif is likely being undervalued right now. Considering this, as well as the strength of its earnings outlook, GEF feels like a great value stock at the moment. Zacks Names "Single Best Pick to Double" From thousands of stocks, 5 Zacks experts each have chosen their favorite to skyrocket +100% or more in months to come. From those 5, Director of Research Sheraz Mian hand-picks one to have the most explosive upside of all. You know this company from its past glory days, but few would expect that it's poised for a monster turnaround. Fresh from a successful repositioning and flush with A-list celeb endorsements, it could rival or surpass other recent Zacks' Stocks Set to Double like Boston Beer Company which shot up +143.0% in a little more than 9 months and Nvidia which boomed +175.9% in one year.Free: See Our Top Stock and 4 Runners Up >>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 Greif, Inc. (GEF): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research