You have to be talented first of all as either a writer or an illustrator and then mail submissions to DC or Marvel comics for review one would assume.

write. Sounds stupid but is paramount. And don't write the same story again and again. Write about every possible genre and every set-up you can. I'm not saying be great at them all but at least try so you can understand the dynamics of each. Next up is read. It goes hand in hand with writing! Pick the books for screenplay writers to understand three-act structure and telling a story visually. I find that understanding how to write a movie is invaluable to writing a comic book. A great book is Story by Robert McKee. Or the webiste wordplayer.com which has some fantastic tips (for screenwriters in specific but good for all writers) and some great stories if nothing else from the world of Hollywood. There are many more sources obviously. There are also books such as "Writers on comic writing" but these are more how they write rather than how-to write. Nevertheless they may give you some insight. marvel and DC bought have some books on the subject but I again stress that the books on film writing are invaluable. Finding your style is important (Writers on Comic writing is a good way of helping you catagorise yourself), as there is no 'right' way to write a comic book. The 'Marvel Way" is usually to write the story and let the artist take over. DC, and people like Alan Moore prefer to write out each page in detail telling the artist what they want and expect. you have to find what works for you and having another person as an artist, even if its just for both of you to practice, is a great way to teach yourself the best method that works for you. On the academic side, course in writing, english and so forth should be readily available. After that sending some samples off to ALL the publishers is important (not just the Big Two) as some are more niche markets that your style may appeal to more readily. Image comics has an excellent open door policy for new artists and writers (check the website). It may also help to have previous work to show rather than just a portfoli you have of 'stuff'. Articles you have had printed in local papers, or a novel you may have actually had published, hell even a script you have sold to Hollywood! Even these on a lesser scale can be important; writing a short film for a local indie movie. Writing a underground comic with friends or locals and so. Well I've gone on long enough.... Good Luck