Every single day since 2014 I log onto DomCop.com and look for valuable expiring domain names. Literally. I've found so many great domains there that I've either put into my domain investing portfolio, built on and created a revenue generating site that I later sold, or used in my efforts to create other valuable websites. I cannot recommend this tool enough--it is robust and powerful, and I easily filter out the thousands of terrible expiring names to consistently find the diamonds.