Start with the ABC's of WCF
http://msdn.microsoft.com/en-us/library/aa480190.aspx#introt_topic2[
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A" stands for Address: Where is the service?
"B" stands for Binding: How do I talk to the service?
"C" stands for Contract: What can the service do for me?
After you get a basic understanding of ABC's go through the below article which has a sample too.Article will help you to understand how ABC's are applicable while developing the service.
Creating and Consuming Your First WCF Service[
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