Dennis grew up in Clinton, Indiana, and attended Indiana University and Indiana State University (cum laude), where he obtained a B.A. in sociology and political science, with a minor in business and economics. Dennis earned his Juris Doctorate in 1974 from Indiana University Indianapolis Law School.

Dennis is somewhat of a rarity among attorneys. He brings a great deal of "real world" experience to the practice of law. At age 17, Dennis worked for Houston Construction Company building gas pumping stations for Tenneco in Staples, Minnesota. At age 19, Dennis worked for Houston Construction Company in Hattiesburg, Mississippi, as an iron worker. Thereafter, he worked at U.S. Steel driving a charging crane in Gary, Indiana. At age 22, he successfully ran a clothing business for five years before going back to school to obtain his undergraduate degree. Thereafter, Dennis went to Indiana University School of Law in Indianapolis and graduated from law school in two and a half years. These experiences help Dennis understand the day-to-day grind that working people endure and the problems small business owners experience in owning and operating a business.