Even more useful than gathering a testimonial you can quote is asking that the reference be passed on. Tell two or three of your business associates how happy you are with our work. The client did. If memory serves me right, that one client gave us four new business leads that resulted in new clients. Ask for introductions to other division heads.
Most businesses nowadays have several divisions that work like independent profit centers.
Once you have done successful work for one division, ask to be introduced to other division heads in the same organization. Make your current clients look good in seminars. Get their permission to use the work you've done for them as case studies. Be careful that you keep sensitive information confidential. At seminars, you can use those case studies to make your clients look good.