Where can you find a job as a graphic novel artist?

Very few people who do this sort of work, have a job doing it. They create works "on spec" and send it around to agents and publishers, and hope someone likes it. Or they publish it themselves through lulu.com or similar services, or as ebooks, or as webcomics. They find their own collaborators (writer and colorist in this case) and just do it.

Since this type of work is so goddamn much fun, the very few salaried jobs and long-term contracts are hotly contested. Employers can afford to be picky. They'll choose someone with "chops" -- a professional with a track record of Excellent work and completed projects. They don't run a classified ad -- they'll contact someone they know, or know of, and offer it to them. It might not seem fair, but that's how the business works.

So whether you mean to find a job, or prefer to remain independent, the way to become successful is the same as for any other art: start doing it on your own. Start a webcomic. Gain a following. Publishers LOVE to work with people who already have a crowd of people who'll buy whatever they produce. Go to conventions and network like crazy, but talking about your work should be less than 10% of that. Get to know people. Look for opportunities. Help others. Run workshops.