Submission Guidelines....

When the time comes, and you feel that your script and/or collaborative project is ready to shop around, this link might well be of some aid.

http://www.optimumwound.com/the-submission-guidelines-for-every-comic-and-manga-publisher-in-the-universe.htm

The folks who maintain it try to keep it up to date. However, should you run into a dead link on their page, don't just give up. Go to the main page of whichever publisher you're investigating and poke around. Don't let Error 404 stop you in your tracks.