So you wan’t to start creating Web Api apps and you don’t have Visual Studio 2012 yet, no problem. You can start using it with Visual Studio 2010. Download http://www.microsoft.com/en-ca/download/details.aspx?id=30683 and install and you’ll have MVC 4 available side by side with MVC 3. You’ll be able to create an MVC4 project.
After that, check out the training videos and other resources here.