While the proven Zacks Rank places an emphasis on earnings estimates and estimate revisions to find strong stocks, we also know that investors tend to develop their own individual strategies. With this in mind, we are always looking at value, growth, and momentum trends to discover great companies.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 tried-and-true metrics and fundamental analysis to find companies that they believe are undervalued at their current share price levels.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 to watch right now is Northern Oil and Gas (NOG). NOG is currently sporting a Zacks Rank of #2 (Buy) and an A for Value. The stock is trading with P/E ratio of 2.96 right now. For comparison, its industry sports an average P/E of 4.89. Over the past year, NOG's Forward P/E has been as high as 6.09 and as low as 2.65, with a median of 3.66.Finally, investors should note that NOG has a P/CF ratio of 5.65. This metric takes into account a company's operating cash flow and can be used to find stocks that are undervalued based on their solid cash outlook. NOG's current P/CF looks attractive when compared to its industry's average P/CF of 7.16. Over the past 52 weeks, NOG's P/CF has been as high as 50.89 and as low as -10.13, with a median of 6.70.Investors could also keep in mind Stone Energy (TALO), an Oil and Gas - Exploration and Production - United States stock with a Zacks Rank of # 2 (Buy) and Value grade of A.Additionally, Stone Energy has a P/B ratio of 1.53 while its industry's price-to-book ratio sits at 3.01. For TALO, this valuation metric has been as high as 2.99, as low as 1.05, with a median of 1.63 over the past year.These are only a few of the key metrics included in Northern Oil and Gas and Stone Energy strong Value grade, but they help show that the stocks are likely undervalued right now. When factoring in the strength of its earnings outlook, NOG and TALO look like an impressive value stock at the moment. Special Report: The Top 5 IPOs for Your Portfolio Today, you have a chance to get in on the ground floor of one of the best investment opportunities of the year. As the world continues to benefit from an ever-evolving internet, a handful of innovative tech companies are on the brink of reaping immense rewards - and you can put yourself in a position to cash in. One is set to disrupt the online communication industry. Brilliantly designed for creating online communities, this stock is poised to explode when made public. With the strength of our economy and record amounts of cash flooding into IPOs, you don’t want to miss this opportunity.>>See Zacks’ Hottest IPOs NowWant 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 Northern Oil and Gas, Inc. (NOG): Free Stock Analysis Report Talos Energy Inc. (TALO): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research