I have no artistic capabilities, so I posted ads on a bunch of artist and pixel art forums looking for an artist. I received many replies, and now I'm working with a very talented and professional pixel artist for revenue share!
When posting, be sure to sound professional (well organized post, no spelling errors, no fluff, points are clear) and post a link to a playable alpha build with placeholder art so the artists can get an idea of what to expect.
If you do get multiple replies to an ad, be sure to keep the connection open and save their contact information in case your current artist abandons the project (50% will).
The same principles go for other departments as well (sound FX, music, etc.).