Like me, you probably really like computer and video games, and have some great ideas for your own games. Let me show you how you can get started doing exactly that. But first you should make an important decision: Are you an artist or a programmer? Artists design the levels, the characters and objects, while programmers turn them into something playable. If the idea of sitting behind a computer till 3am, trying to make a piece of code work doesn't excite you, skip to step 4.
Things You Will Need
First you'll have to choose a programming language you want to learn. The standard language in the industry
is C++. Most games
are written in it. C++ has the disadvantage that it is hard to master. You could start with an easier programming language like C# or Python and then move on to C++. This How-to will not teach you any programming language, but once you've picked one, you'll find that there are tons of tutorials online.
As soon as you feel like you're pretty good at programming, you can start thinking about making your own 3D game. You'll need a game engine, a programming library that enables you to draw graphics, use input devices, play sound, etc. You could make your own, but let me warn you that it will take very long because of all the things you'll have to learn. The alternatives are 3rd-party engines available for use by anyone: OGRE3D, Unity, Unreal Development Kit, to name a few.
With your programming knowledge and a game engine, you can start coding your own game. You'll need to know your engine, so if you chose an existing engine, read the tutorials and documentation. Then you'll need to look into actual game programming topics; the architecture of a working game. That stuff fills many books, and while that would probably be the quickest solution, all the information is on the internet. Read about it here
if you are interested.
You've probably realized by now that programming a game is a very long and complicated process, which is usually done in large teams. As a programmer however, you have the most power when you're making your own game, if you're also a talented artist. If you're only interested in creating the art for a game, you should look for open source game projects and ask them if they need any help.
Tips & Warnings
Creating a game like Halo or World of Warcraft requires a team of more than a hundred people and it takes them years.