Stephan Schiffman has trained more than 500, 000 salespeople at such firms as AT&T, Information Systems, Chemical Bank, Manufacturer's Hanover Trust, Motorola, and U.S. Health Care. Schiffman is president of D.E.I Management Group and the author of such bestselling books as Cold Calling Techniques (That Really Work) and Closing Techniques (That Really Work) as well as The 25 Most Common Sales Mistakes, also published by Kogan Page.