I've been working as a game designer myself for some time so I wanted to share my experience of it and give some insights.
What are the requirements?
There is no precise set of requirements for becoming a game designer. Most designers come from different fields of computer arts, programming or directly out of QA and I could totally see people from science or psychology fields orienting themselves in the video game field. In fact, the more diverse are your knowledges, the better.
The first thing to do is to ask yourself “what kind of games I want to design?”. A lot of big companies are breaking down the designer's job into sub-categories like “sports game designer”, “FPS designer” or others. But this is not all. You don't have to work for one of the big companies to work as a game designer. There is a whole independent (indie) scene getting larger than ever, the casual web game scene, ludo-educative games and an emerging serious games scene too. There is probably a lot of other opportunities that I'm not even aware of but let's look at those first.
The big players
Here we have the likes of Ubisoft, Electronic Arts, Gameloft, Eidos and other huge studios that concentrate on getting as much games out as possible with the highest production value possible. I've been in one of these companies before. While working on the latest cutting edge next-gen game might sound very exciting, you must be ready to put in some time and effort as these companies are habitually very demanding toward their employees (check out the EA spouse web site http://ea-spouse.livejournal.com/274.html to see what I mean). I've known people who were happy to work for those big corporates and pull those huge next-gen games but, for myself, I quickly got tired of the long hours and the low rewards. However, if you are new to the game field, it might be your best chance to get a designer job as they hire a lot of young talent. From my experience, employees would stay in that kind of company for an average of 2 years, so this opens up for a lot hiring in the long term. Just show them you know what you are talking about and that you are motivated and ready for the wild ride, and it should be enough to get you in somewhere (be it game designer, level designer or integrator. Integrator can be a great starting point).
The indie scene
Independent development is a lot more risky since it is often paid on short contract and you have no warranty that a game will sell. I would not recommend starting your own company if you have no experience, though getting a couple of contracts will help you see what the indie scene is all about. Check out forums http://forums.indiegamer.com/index.php for informations and job offers. While there is a lot of risk at sake (ie: how much food there is in your fridge) being an indie developer is extremely involving and exciting. You get to work on the projects you believe in, you have a lot of responsibilities regarding the quality of the game, it's marketing and customer support, there is no boss over you head to tell you what to do. Basically; you get the freedom to do your things. If you have enough talent and are ready to risk a part of your income, I'd say go for it.
Being an indie developer also means that you'll have to wear a lot of different hats. Most of the time you will be working with a very small team so the more you know about coding, art, sound and design, the better. These days, some online publishers are emerging to help the indie scene. The most important one is probably Manifesto Games that concentrate on hardcore games of different genres but there is also Kongregate which wants to be the YouTube of Flash games. The advantage of these publishers is that they pay a good percentage to the developers.
What some call the “thirty-something-at-home-mother's games”, though this is somewhat totally inaccurate and limiting. This particular market mostly started out with independent developers building simple and addictive puzzles games but it grew to a point that now there is big players in it; Shockwave games, Big Fish Games, Reflexive Arcade, Real Arcade and a lot of others. Those are all massive publishers or game portals. A lot of the games are still developed by independents and sold to the portals for distribution. Developers are paid based on the number of game sold but the margins have gotten a lot smaller as time passes and the popularity of the portals goes up. While you might not get a lot of money on each single game sold, the big advantage of these portals is that it gives you a huge amount of visibility.
This is where I work right now. I'm working for a company that develops educative games for young children. I have not heard about a lot about these companies as there is few of them but from where I work, I can tell that the quality of life in these environment is much higher than with the big players. First of all the company is much smaller, which gives place for more discussion and employee empowerment. I'm not doing any overtime and if ever I have to (in exceptional occasion) I'm paid for it. My bosses care about their employees and the environment is much more relaxed. I'm really enjoying my experience so far and the games are of tremendous quality.
The big difference with the children's games market is that while the profit margin per game is somewhat lower than the next-gen games, there is a lot less competitions and a single game can sell for several years. Children do not care about having cutting edge technology graphics and they are not consuming dozens of games every years like the average hardcore gamer so a single game has a lot longer shelf life. This reduces the pressure on a company and, consequently, on it's employees.
This might be the kind of games I'm the most interested in but at the same time it's the domain I know the less about. Indeed, this is a very new domain. Academics and searchers are realizing that games have tremendous power for teaching and they are trying to put them to good use for the society. This includes games for education, training in various fields, health, politics, etc. These games can range from simple trivia to complex simulations. I encourage you to discover this field. There is some very entertaining games that gets you thinking (like 3rd word farmer that I have talked about in a previous post).
Here is some other links on the subject:
Social Impact Games
Serious Games Initiative
I could not tell exactly what it takes to get into this business but it appears that a lot of games are produced by companies outside of the game industry and by universities. I've seen universities offering open calls to developers for making particular games with social impacts so there is certainly some openings for independent developers as well.
So what now?
Once you found where you want to belong, I recommend that you read as much as you can on the topic of your interest. If you are interested in the big players or the casual game space, play a lot of those games and find out what it is that interest you. What are the strength and weaknesses of those games? Why do you enjoy them so much? Study their design (levels, mechanics, controls, interfaces, characters pace).
If what you are really interested in is the AAA games of the big players, you better break down to what really resonates with you. Would you rather be a level designer or a script writer? Do you want to build game mechanics, artificial intelligence, stories, interfaces? As these companies get bigger, the jobs are getting more specifics so it would be good if you knew what you want to do exactly, or at least what you want to specialize in (as you are always likely to wear more than one hat).
If you are interested in serious games or ludo-educative games, read on the subject and check out what has been done. While there is not a huge amount of serious games, the domain is well documented and you can already ask yourself what is the statement you want to make by developing a game. Surely it will be about a well known topic that is already strongly documented like health or politics. How can you apply interactivity to it and how is the interactivity meaningful? More than often it will be a big challenge as it is most probably something that has never been done. Educative games often bear the same kind of challenges; you have to learn about education, school programs, learning methods, etc..
And whatever the kind of games you want to build, do you want to work for someone else? Would you prefer working in a big or small company? Or would you rather go out on your own and try to do it by yourself?
Yet, if you really want to be a designer, whatever in which field, there is a lot of basic stuffs that you need to know and there is a lot of books that can help you.
Here are some recommended read on design topics:
A Theory of Fun
Fast and fun read. Simply thought provoking.
Rules of Play : Game Design Fundamentals
Katie Salen and Eric Zimmerman
A lot of strong theory and very practical tidbits and experiments. Very academic book. Strongly recommended.
Rollings & Adams on Game Design
Though a bit too general to dig in anything specific, this book comes as an excellent overview of the established genres and basic design consideration. I would recommend this one as a good starting point.
Better Game Characters by Design
I have yet to read this one. Tell me what you think if you've read it. :)
Though this book is about comics, I found that most concepts can be applied to telling stories in a game. From building worlds and characters to developing the pace and a graphical style, this is all amazing stuff.
Joel de Rosnay
This is a scientific vulgarization book. Rosnay explains how different complex systems (human body, economic systems, corporate environment..) work and are regulated (or balanced). This is crucial theory if you want to build good simulations.
The book can be read online for free (the original version is in french but the link is for an english version).
Becoming a game designer is a lot of work. It is an art in itself and must be taken as such. But it is also a lot of fun and seeing your game getting built is very rewarding. If you have any other read recommendations or something to add on any topic of this article, I'd be pleased to read about it so go on and comment! :)
[UPDATE: If you want to learn more, you can read the follow-up to this article: "How to become a Game Designer? - My career story"]