Simple JSON request

Hi,
I'm trying to make API calls to a service provider. I've never tackled JSON requests before but I want to give it a go - as they seem less verbose than XML. Could someone be kind enough to give me a simple example here? 
My confusion stems from some libraries I've come across. Do I need to add any libraries to my project? Or is it just a matter of creating a string that complies with JSON syntax and send it via a WebRequest?
...