Things You'll Need
Instructions
Note that you need to be familiar with Microsoft's Visual Studio, as well as be fluent in Visual C# programming. Make sure your PC meets the basic requirements---Vista or XP Service Pack 2 plus a video card that supports DirectX 9.0c with shader model 1.1, the graphics toolkit responsible for special visual effects.
Join the XNA Creators Club at xna.com and sign up for full membership. Download the latest version of the XNA Game Studio software suite. Also make sure to download the latest versions of Visual Studio and Visual C#, which integrate with the XNA software, as well as both the DirectX development kit and runtime Web installer. All of these downloads are free from the Microsoft website.
Purchase a premium membership at the XNA Creators Club after making sure all of the software was downloaded properly. Although XNA itself is free, it does require paid membership in order to sell games developed for the Xbox 360 on the Xbox Live Marketplace.
Develop your game within the Visual Studio and XNA Game Studio environment. Keep in mind the game engine and programming are all up to your skill level with Visual C#, as XNA does not do any of these automatically like traditional game engines such as Unreal 3 and Chrome 4.
Test your finished game on your Xbox 360 console, Zune or Windows PC. The XNA Game Studio suite has functions designed to "finalize" games for transfer to these devices. Make sure all errors and glitches you can find are worked out prior to the next step. In other words, the game must work as intended.
Submit the finished game as a .ccgame file to the XNA Creators Club; further submit it to the Xbox Live Marketplace, if it's an Xbox 360 title. Be prepared for a lengthy peer evaluation process undertaken by other XNA creators, plus a certification process by Microsoft if you want to sell the game on Xbox Live. Games can't be published or shared with others without this approval stage, but may be kept for your own use.
Decide whether your game will be for Xbox 360, Zune or Windows PC before proceeding.
Development time is entirely dependent on your own skill and ambition---most XNA titles currently available have taken a few months to create, with teams averaging five members. This is noticeably different than full commercial games, which take around a hundred people and more than two years on average.