1. Be a remarkably talented writer. Frankly, like me, you could get away with being competent with a bit of personal flair, provided you also have a bit of luck and know games inside out. But if you're a naff writer - if you've not written for yourself, or braved honest critique with your work - that's your first stumbling block. Being fantastic will help lots.
2. Understand games. Playing lots of shooters probably isn't enough. You've got to think about games critically as any developer would - that's what makes you a narrative designer, not just a hired hack.
3. To those ends, play lots of games, read lots of books. Think about them. Write about them.
4. Keep trying, take anything, try everything. Build an indie game, write for a mod, write reviews, email devs, work in QA, build a portfolio.
5. Network. Doesn't matter what route you come into the business through, getting jobs - particularly writing jobs - isn't always a case of seeing an ad and sending in your CV. Go to events, buy people beer, bum a cigarette, blog, twitter, remind people you exist.
6. Network. Seriously. 70% of my work comes through networking and repeat custom. The rest is through my fabulous agency (who, I'm afraid, only consider established professionals). Can you guess how I got in touch with my fabulous agency? Networking.
The routes in...
7. Be a professional writer in another medium. Sounds like a big ask, but look at it this way: every medium other than games is better equipped to recognise and reward writing talent. Books and comics in particular are far lower cost, and have more releases every year - and therefore have more demand for good writing. It'll still require excellent networking to make the switch, though.
8. Move roles within the games industry. Entry level positions in production, level design and QA are all realistic goals for a talented writer and, with some careful planning and a constant eye on opportunities within the company, can be converted into a writing role - either over time by picking up basic writing responsibilities, or as a direct move. Do note, though, that telling your seasoned QA manager that you're only there to get a 'proper job' is most likely a poor idea.
9. Get in with the indies. This was my route. Working on something amateur is very easy to get into (by comparison to, say, writing a novel). Do it enough and one of them might turn pro. Congrats - you've got your first professional writing credit! Now go network!
10. Learn from my mistakes.
DO email loads of devs (ideally smaller ones in less established territories like eastern Europe) out of the blue telling them how much you love their games (if you do) and how you think you can help. I must have sent hundreds of prospective mails before I got my break on Penumbra.
DON'T piss people off with spam.
DO keep trying.
DON'T keep trying if everyone (even your mum) tells you your writing is shit. It probably is. Play to your strengths.
DO realise that being a video game writer is one of the most sought after jobs on the planet because it's one of the most amazing jobs on the planet.
DON'T forget that if you're a fantastic writer you're already ahead of 90% of your competition.
This post remains the most hit page of this blog, so I can only figure a lot of you are landing here from google searches and whatnot. Hello, I'm Tom.
If you'd like more help and resources on how to get into this line of work do leave me a comment down below and I'll get back to you. I also recommend you check out the list of narrative design resources (design docs etc) listed on this very site!
You may also find some of the other posts on this blog of use. Some good places to start are the Development and Advice tags.
I went to a BAFTA games writing event recently at the ICA to have a meeting with my agent and Charles Cecil, and met a chap from the drama industry looking to break into games. I wrote him out some good places to start looking for small indie teams and while I'm sure a lot of my readers will be familiar with these already, they may prove useful for anyone referring back here in the future.
http://forums.tigsource.com/index.php Indie dev forums with lots of work-in-progress and volunteer request threads. Just be aware that most are ludicrous pipe dreams; steer clear of the one-man-MMOs.
http://www.gamasutra.com/jobs/ I've seen the odd small / cheap writing job go up on these boards, worth posting a profile at any rate.
http://www.moddb.com/ Home of work-in-progress mod projects, some really good stuff here.
http://www.igf.com/ Competition for the very best indies, should give you a picture of who's big at the mo.