Value proposition is a promise of value to be delivered and acknowledged and a belief from the customer that value

Creating a Great Value Proposition
"Why should I buy this specific product or idea?" asks your customer: And your value proposition must answer this, in a compelling way. In creating a good value proposition, the trick is to know your product or idea well, know how it compares with those of your competitors and, very importantly, put yourself in your customer's shoes to find the answers.
Your value proposition can be created step-by-step, by answering a series of questions. Once you answer these, you have the ingredients to create a value proposition that answers your customer's question: "Why should I buy this product or idea?"
Creating a Value Proposition
Communicating the Benefits of Your Product, Service or Idea, Simply and Clearly (Continued)
http://www.mindtools.com/CommSkll/ValueProposition.htm
Step 1: Know your customer
Thinking from the perspective of your customer, ask the following:
Who is he or she? What does s/he do and need?
What problems does s/he need to solve?
What improvements does s/he look for?
What does s/he value?
Tip: If you don't know, ask! It's easy to try to second guess what your customers want. And very easy to get it wrong.
So do some market research: This could be a simple matter of asking customers directly, or organizing a focus group or surveys. 'Market research' is not just for external customers, it works for other 'markets' too: Depending on your product or idea, your 'market' could be employees, colleagues, or even your spouse.
Step 2: Know your product, service or idea
From your customer view point:
How does the product, service or idea solve the problem or offer improvement?
What value and hard results does it offer the customer?
Tip: Include numbers and percentages
To grab your customer's attention even faster in this financially-oriented world, your value proposition should also speak percentages and numbers: How much will your customer gain, save or improve? How much more efficient will he or she become? How much safer, smarter, faster, brighter will the solution be? And so on.