So you would like to create a machinima? Creating a machinima takes time, creativity, and effort. You can't just say "I want a machinima!" and POOF! A machinima will appear. It is a lot more complicated. This guide will help simplify the process for you.
So starting off a machinima. The very first thing to do is have an idea for a good series. You should also decide what game engine you will use. It is important that you know what game engine you plan on using so that you are aware of the limitations you will have, and obstacles you may face. You should go to the Game engines article to help figure out what engine to use.
When considering what engine would best fit your purpose, be aware of that engine's modification ('mod') possibilities. These will greatly enchance your vision if avalible, as you will be able to create what you need if the tools or SDK (source development kit) allows it.
Now you've got a great idea and an amazing game engine to work with. What you will need next is a script. For a successful series it is necessary you know how the storyline will work out, to keep control of your ideas and to avoid plot holes. You can write your script in any word processing program. You can use Microsoft Word, Notepad, Open Office, etc. Another option is to get a program specifically to write scripts, such as Celtx, which could be found at http://www.celtx.com. This program will allow you to easily make a script in the standards that have been set in the movie business. To top it all off, the program is free (another software is Final Draft, but that is not free)! SO now that you've gotten your script, you need to think about the next step: Filming
So how do you film your game? Well it really depends on what platform you're using. If you're using a console game you'll need a Video Capture Card, also known as T.V. tuner card. If you're recording a PC game you'll need a capture program like FRAPS (http://www.fraps.com).
Once you have the footage you need, it is time to piece it all together in an editing program! Free video editing programs include Windows Movie Maker, which comes with any version of windows (even Vista, just look in Program Files and search for Movie Maker) and iMovie, which comes with newer versions of Mac OS. Another option is to use a more high end editor like Adobe Premierefor PC or Final Cut for Mac. While these programs are expensive, and a little complicated, they will help give you a better end result.