To go through the user manual, you need the following:
A working understanding of Revit Architecture 2013, Revit Structure 2013, or Revit MEP 2013.
Familiarity with a Common Language Specification compliant language like C# or VB.NET.
Microsoft Visual Studio 2010, or Microsoft Visual Studio 2010 Express Edition. Alternatively, you can use the built-in SharpDevelop development environment in Revit.
Microsoft .NET Framework 4.0.
The Revit Software Developer's Kit (SDK) which you can download from the Autodesk Developer Network (ADN) or the Revit installation CD/DVD (<DVD_Drive>:\Utilities\Common\Software Development Kit).