If I had a penny for every time I’ve been asked this question…
Game developers have only a few broad types of employees. Excluding administrative ones like office management, HR, and IT, broadly the team has Programmers, Artists, Sound Engineers, Game Designers, and Testers (some also have Producers, but at Naughty Dog we didn’t believe in them, so we distributed their work among the team leads). Of these jobs, only “Game Designer” is “purely creative” per se. Truth is, on a good team all game jobs are creative, but designers are alone in that they don’t have a craftsmany trade.
Programers can write some other kind of application and demonstrate their coding skills. Artists can show off awesome models, animation, textures, lighting, sketches etc. Externally, at home or school, an artist can learn to use art tools to build good looking art. It can be seen. He can say, “I modeled all of that in 2 weeks, although my friend did the textures.”
Game designers have to learn on the job. While all good game designers LOVE video games, not all lovers of video games make good game designers. There are different sub-types of designer, and all of them require many specific skills and personality traits. Creativity, organization, obscene work effort, organization, creativity, organization, organization, cleverness, willingness to take a beating, willingness to stand up for and demand what you believe is good, grace to admit when you idea sucked ass.
So how do you learn this stuff? How do you demonstrate it to a prospective employer. Tough.
Some you learn by playing insane amounts of games. Better yet, you make games. But… unlike a programmer or artist, it’s kinda hard for a designer alone to make anything. So you need to hook up with a great artist friend and a great programmer friend and make something cool. There are school programs now for this too, but the projects don’t have the sustained scope, scale, brutality, hideous cruelty, pain, and near death quality that real game development has. No. Not even close, not even a tinsy bit.
An old method was to become a game tester, and hope that the brass would notice your organizational skills, creativity, etc and promote you to a junior designer position. Probably this will sometimes still work. It requires a lot of stamina and a high tolerance for day-old hot wings, dirty bare boy-feet, and stale crispy cremes. But then again, if you can’t stomach that stuff you don’t belong in games.
You could also try and grab some kind of coveted internship and try to prove yourself. Also requires extremely high self motivation. Then again, if you don’t have that than forget trying to be a game designer anyway.
Maybe the bigger companies take junior designers with no experience. At Naughty Dog we never did.
But it’s still possible with an artist friend and a programmer friend to make a cool iPhone / Flash / etc. game. Do it. Do it again. Do it again. Do it again. Do it again. When a couple of them are good, you’ll find a job.