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.Looking at the history of these trends, perhaps none is more beloved than value investing. This strategy simply looks to identify companies that are being undervalued by the broader market. Value investors use a variety of methods, including tried-and-true valuation metrics, to find these stocks.In addition to the Zacks Rank, investors looking for stocks with specific traits can utilize our Style Scores system. Of course, value investors will be most interested in the system's "Value" category. Stocks with "A" grades for Value and high Zacks Ranks are among the best value stocks available at any given moment.One company value investors might notice is Allstate (ALL). ALL is currently sporting a Zacks Rank of #2 (Buy), as well as a Value grade of A. The stock has a Forward P/E ratio of 8.64. This compares to its industry's average Forward P/E of 24.57. ALL's Forward P/E has been as high as 12.14 and as low as 7.06, with a median of 8.56, all within the past year.We also note that ALL holds a PEG ratio of 1.15. This popular metric is similar to the widely-known P/E ratio, with the difference being that the PEG ratio also takes into account the company's expected earnings growth rate. ALL's industry has an average PEG of 3.40 right now. Over the last 12 months, ALL's PEG has been as high as 1.46 and as low as 0.85, with a median of 1.14.Value investors also use the P/S ratio. The P/S ratio is is calculated as price divided by sales. Some people prefer this metric because sales are harder to manipulate on an income statement. This means it could be a truer performance indicator. ALL has a P/S ratio of 0.74. This compares to its industry's average P/S of 0.97.These figures are just a handful of the metrics value investors tend to look at, but they help show that Allstate is likely being undervalued right now. Considering this, as well as the strength of its earnings outlook, ALL feels like a great value stock at the moment.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 The Allstate Corporation (ALL): Free Stock Analysis Report To read this article on Zacks.com click here.