There are several requirements for designers that are non-negotiable. Without these skills you can pretty much forget about even bothering to become a designer, as you're not going to be able to do your job effectively.
This is the big one. Forget about having tonnes of ideas - ideas are worth nothing unless you can communicate them to the world. Design is in its purest form communication of an idea and nothing else.
There are two groups you need to converse with - your team and your audience.
Conversing with your team can take a number of forms - not every designer is born equal in communication skills. Some are verbally adept. Others are better at communicating through the written form. Others may have visual design skills that communicate best through images. Whatever the form of communication - there must be at least one clear method that demonstrates this communication skill. If you are bad at verbal forms of communication then it can make interviews pretty tough. My suggestion in this case is to be honest - tell your potential employers that your communication skills are better served through other methods, and provide examples.
Conversing with your audience is a little different. A good designer doesn't just design games for themselves. They must understand the commercial realities of the market. They must be ready to engage in user testing - gaining data from their audience and interpreting it in a way that will benefit the game. Good games are very, very rarely designed in a vacuum - that is to say that everyone needs feedback and critique.
2. A Lack of Preciousness
This may at first seem odd. Shouldn't I champion my ideas? Should I not defend them? Simple answer - no.
A good designer will be willing to collaborate. They are willing to listen to everyone's ideas (no matter how daft they may sometimes seem). They act more as an arbiter of ideas, filtering out elements that work from those that don't.
In regards to their own work, they must be open to critique and be ready to change and improve upon what they have done. If you feel really strongly that something is the right direction and it is being challenged, the best possible advice I can give is pick and choose your battles. If you defend every single idea you have, there is no room for maneuver. If you carefully consider which ideas are worth holding onto - then you are compromising - and compromise is an essential part of collaboration - it shouldn't ever be seen as "giving in".
3. Passion for Games
There's no doubt that without a passion for games, then there's no point in becoming a designer - you simply won't enjoy the job.
This passion should extend beyond a small subset of games, otherwise you end up becoming too narrow minded. There is potential for the spark of an idea in all genres - new mechanics, ideas for scenarios, enemy types, etc.
But don't play games at the exclusion of all other information. This leads neatly into the next requirement...
4. Passion for Information
A good design has a thirst for knowledge that is almost impossible to quell. They should want to learn about almost every subject, since there is something of use for any designer.
Doing research is an essential part of developing a good game - and learning about history, geography, math, etc will ensure that the designer is rounded enough to think about things from many different angles. You can always tell when the design of a game has had a poor background in research - even the smallest detail being wrong can lead to obvious holes for your audience.
So get reading - the internet is the most incredible invention for human knowledge in our entire history. Use it, but remember that not everything you read is correct ;)
The Advantageous "Qualifications"
So the essentials seem a bit intangible? Yes - that's because the essence of a designer is fairly intangible. I've worked with designers from all types of backgrounds:
- Computer Science graduates (of which I am one)
- Modders (of which I also am one)
- History graduates
- English graduates
- Physics / Philosophy graduates
- Engineering graduates
- Game Design graduates
All of these are perfectly valid for designers, but guess which ones have the toughest time getting game design jobs? It might surprise you, or might not, but Game Design graduates are less likely to get the job than the others. There is a large amount of disdain for Game Design courses within the industry, except from a select few colleges / universities (such as Carnegie Mellon or University of Abertay). So what do we look for in designers?
1. Academic Qualifications
Like it or not, Acadameic qualifications are extremely useful (but not essential I might add). They show employers that you have the ability to work at a certain level. They show you have applied yourself to a subject and potentially mastered it. They show that you have a thirst for knowledge. As mentioned above though - the type of qualification is important. Don't do a "bums on seat" degree like Media Studies - and if you are going to do Game Design, ensure that you do it to build you portfolio, because the qualification isn't going to get your foot in the door as courses currently stand.
I'd actually suggest doing something more like Engineering, Computer Science, Product Design or Architecture, as these teach you skills that you are going to be learning on a daily basis, but aren't as narrowly focused as a Games Design degree (also if you don't get in the industry you have a fallback plan, because a Game Design degree will get you laughed out of most "serious" jobs).
This is the single best way of getting in the industry - since it proves several things - a passion for games, an aptitude for creating things and the self motivation to do your own work. The major benefit of this is it also builds your portfolio for when you decide to apply for a job in the industry. Just remember when applying for jobs, that the way modders work and the way professionals work is very different.
If you want to start modding, pick a game you enjoy and go from there. These days its a lot easier than when I started back in 1998 - since you can pick up a copy of UDK or Unity and create your own games with relative ease.
3. Extra Curricular Interests
Don't just play / make games - this makes Jack a dull boy. You need to be rounded in your interests - as mentioned above - you need to have a thirst for knowledge.
Play sports, learn an instrument, read books, watch movies, go hang-gliding or cook food. Do something that ignites your passion beyond just gaming. This is more important to an employer than you can possibly imagine.