My recommendation is to become an expert (at least in the prospect's eyes) at what you do and impress them that way. Forget about the "just go out and sell" advice UNTIL you become an expert. Then you can sell them on your honesty and willingness to do what it takes to get their business. Also, ask them about when they first started in business and didn't have any clients and how they did it.
Take the time to build relationships and trust. This strategy will take more time and effort but will pay off.
If you use "I've got confidentiality agreements with my clients" or any of those other deceptive "strategies", what are you going to do when they say, "I understand, you don't need to give me names but tell me what you are doing/have done for them? And when did you start working with them?" You will have to continue the lies and will probably be found out.
Word gets around fast so you run the risk of ruining your reputation. Plus this is no way to build trust and start a relationship
I'll be closing a deal shortly (hopefully today) with my first new car dealer and guess what? They never asked me for references, about my experience or any of that. Why? Because I'm an expert...at least in their eyes.
Plus with my strategy you'll be able to sleep better. Take the high road and good luck!