The customers you already have could be your biggest lead source, and you may not even realize it. Think about it this way, ... after more of their business, and that of their friends and family.
I've been hearing for years that a successful business needs to have a USP (unique sales point). The problem is that most businesses ... logical one, whatever they're buying - so what's your ESP?
When it comes to selling your products it is important to ask your potential customers probing questions as well as open ended questions ... your services and refer friends and family to you as well.