Wall Street watches a company's quarterly report closely to understand as much as possible about its recent performance and what to expect going forward. Of course, one figure often stands out among the rest: earnings.Life and the stock market are both about expectations, and rising above what is expected is often rewarded, while falling short can come with negative consequences. Investors might want to try to capture stronger returns by finding positive earnings surprises.Now that we know how important earnings and earnings surprises are, it's time to show investors how to take advantage of these events to boost their returns by utilizing the Zacks Earnings ESP filter.The Zacks Earnings ESP, ExplainedThe Zacks Expected Surprise Prediction, or ESP, works by locking in on the most up-to-date analyst earnings revisions because they can be more accurate than estimates from weeks or even months before the actual release date. The thinking is pretty straightforward: analysts who provide earnings estimates closer to the report are likely to have more information.Now that we understand the basic idea, let's look at how the Expected Surprise Prediction works. The ESP is calculated by comparing the Most Accurate Estimate to the Zacks Consensus Estimate, with the percentage difference between the two giving us the Zacks ESP figure.In fact, when we combined a Zacks Rank #3 (Hold) or better and a positive Earnings ESP, stocks produced a positive surprise 70% of the time. Perhaps most importantly, using these parameters has helped produce 28.3% annual returns on average, according to our 10 year backtest.Most stocks, about 60%, fall into the #3 (Hold) category, and they are expected to perform in-line with the broader market. Stocks with a #2 (Buy) and #1 (Strong Buy) rating, or the top 15% and top 5% of stocks, respectively, should outperform the market, with Strong Buy stocks outperforming more than any other rank.Should You Consider Roku?The last thing we will do today, now that we have a grasp on the ESP and how powerful of a tool it can be, is to quickly look at a qualifying stock. Roku (ROKU) holds a #3 (Hold) at the moment and its Most Accurate Estimate comes in at -$0.09 a share 15 days away from its upcoming earnings release on May 6, 2021.Roku's Earnings ESP sits at 48.74%, which, as explained above, is calculated by taking the percentage difference between the -$0.09 Most Accurate Estimate and the Zacks Consensus Estimate of -$0.18. ROKU is also part of a large group of stocks that boast a positive ESP. All of these qualifying stocks can be filtered by ESP, Zacks Rank, % Surprise (Last Qtr.), and Reporting date.Now that you know how to use the Zacks Earnings ESP to your advantage, make sure to check out the Earnings ESP Home Page for even more earnings related strategies to create a winning portfolio.Find Stocks to Buy or Sell Before They're ReportedUse the Zacks Earnings ESP Filter to turn up stocks with the highest probability of positively, or negatively, surprising to buy or sell before they're reported for profitable earnings season trading. Check it out here >>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 Roku, Inc. (ROKU): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research