Here's a very (very!) quick WCF overview I prepared the other day for the team at Zap. It's intended as a soldier's five on the topic; no more and no less.
Service Contracts and Operation Contracts
This is what your WCF service promises faithfully to do for its callers.
These are the data types that your WCF service expects its callers to understand. Thankfully, it will happily explain these data types to its callers.
Events (... or "Duplex Contracts")
Out of scope for this presentation, but see http://msdn.microsoft.com/en-us/library/ms731184.aspx for a pretty decent explanation.
Hosting Your WCF Service
Note the endpoint address:
Adding a service reference to your project
The metadata exchange address is the equivalent of the old Web Service Definition Language (WSDL) address.
Calling the WCF Service
Call it just as you would your local methods.
It's that easy.
Purely for edification, this is what some of the generated code looks like: