 I have a simple yet effective way to screen for potential stocks to buy. If a stock price has dropped significantly, I check the insider buying.Insiders are people who have access to confidential information about the company. It goes without saying that they probably have a much better idea of what is happening in the company than most analysts. They certainly know more about it than I do.Over the years, many insiders have used this information to gain an unfair advantage over uninformed investors. One of the regulations that the SEC has established to prevent this kind of activity is the requirement that an insider must publicly disclose when they have made a transaction in their stock.InvestorPlace - Stock Market News, Stock Advice Trading TipsBecause of this, we outsiders can profit. We can find out if the insiders are buying or selling.There are many reasons why an insider of a company may be motivated to sell their stock. They could need to raise money for things such as buying a house, installing a pool, or paying a college tuition. But an insider will only buy the stock for one reason -- they believe that the stock is undervalued and that it will trade at a higher price, where they can make money. 7 A-Rated Stocks to Buy for the Rest of 2019 These companies are on my radar screen as potential stocks to buy due to the significant insider buying that has occurred recently. Stocks to Buy: Carnival CCLCarnival NYSE:CCL is the popular cruise ship company. It has worldwide operations but the headquarters are in Miami, Florida.CCL has lost over 10 of its value since its June 20 earnings release was a disappointment to investors. Since then, there has been some significant insider buying.Last week, the president and chief executive officer of Carnival, Arnold Donald, made some large purchases of the stock. He invested 1 million when he bought 22,050 shares around 45.31.Mr. Donald also made a similar size investment in December, when the markets made the significant move lower and CCL was trading around current levels. He must believe that the stock is a good value at these levels.Randall Weisenburger is a director of Carnival. He must also believe that the recent selloff is over because he just made a considerable personal investment as well. He just paid 46.50 for 20,000 shares. This is 930,000. Hooker Furniture HOFTHooker Furniture NASDAQ:HOFT is a home furnishings and logistics company. Thats a fancy way of saying that they make and sell furniture.The stock of HOFT has dropped over 50 in the past year. At this time last year it was trading around 48 per share. The most recent close was 21.32. In June the shares dropped from 27 to current levels due to disappointing earnings results. The company blamed it on tariffs and higher lumber costs. 7 Retail Stocks to Buy That Are Down in 2019 Douglas Townsend is the co-president of the Home Meridian Segment of the company. He must believe that this selloff has come to an end. Mr. Townsend just invested over 100,000 when he bought 4,900 shares at 21.64. Nymox Pharmaceutical Corporation NYMXNymox Pharmaceutical Corporation NASDAQ:NYMX is a biopharmaceutical company that engages in research and development of products for the ageing population. This sounds like a great business to be in, but NYMX must being doing something wrong. Over the past year the share price has dropped by 60.James Robinson is a director of Nymox. Mr. Robinson must be tired of watching the stock fall and thinks that this selloff is overdone. He invested 150,000 when he recently paid around 1.50 for 100,000 shares.No firms on Wall Street follow this company. Some investors may consider this to be a good thing because they believe that if they can get into it before it is discovered by the big players, they will be able to make significant profits. Kroger KRKroger NYSE:KR operates various types of stores, including food and drug stores, multi-department stores, jewelry stores and convenience stores.Like many retailers, KR stock has had a rough time over the past year. Shares have lost about 30 of their value since their highs last September. Some blame this on a combination of tariff concerns and the Amazon NASDAQ:AMZN effect.Ronald Sargent is Krogers lead director. He must believe that the recent selloff has created a great buying opportunity. He just invested 107,000 of his personal funds when he bought 5,000 shares at 21.49. 10 Stocks That Should Be Every Young Investors First Choice This is the first time an insider has purchased shares of KR in two years. Maybe this is because the Board of Directors just increased the dividend by 14. Dave Busters Entertainment PLAYDave Busters Entertainment NASDAQ:PLAY owns and operates entertainment and dinning venues. Its concept is to offer customers the opportunity to eat, drink and play in one location.Unfortunately for the shareholders of PLAY, they have not been as entertained as the short-sellers have. Since early May, the price of the stock has fallen by 30. This includes the drop of 20 that occurred when the company missed earnings estimates in early June.Michael Griffith is a director of Dave Busters. He apparently thinks that this recent weakness in the stock has created a buying opportunity. He just invested almost 200,000 of his own money when he purchased 5,000 shares at an average price of 39.31.Currently, 10 firms on Wall Street follow PLAY stock. They like it as well. The average rating is overweight and the average price target is 50. Greif GEFGreif NYSE:GEF produces industrial packaging products and services.In the past four months, the price of GEF stock has dropped from 42 to 34. This has been attributed by analysts to lower volumes of sales in some sectors and higher debt burdens. It could also be under pressure due to worries about tariffs.Peter Watson is the president and chief executive officer of Greif. He must believe that the selloff is over and that the stock will appreciate from here. Mr. Watson just paid 32.71 for 15,000 shares of GEF. That is a 500,000 investment. 7 F-Rated Stocks to Sell for Summer Seven firms follow Greif. Opinion seems to be widely varied. There are three buy ratings, three sell ratings, and one hold rating.As of this writing, Mark Putrino did not hold a position in any of the aforementioned securities. More From InvestorPlace 2 Toxic Pot Stocks You Should Avoid 7 A-Rated Stocks to Buy for the Rest of 2019 7 Education Stocks to Buy for the Future of Academia 5 Stocks to Buy as You Rebalance Your Portfolio The post 6 Stocks to Buy Based on Insider Buying appeared first on InvestorPlace. 