Mainstream Publishing
Some mainstream publishers are reluctant about accepting work from young writers who can not sign a contract. What matters really, is that the quality or standard of writing should be high in order to compete with adult writers. To do this, the important thing is to thoroughly edit your work and follow the submission guidelines set by the publishers.
Some publishers prefer that you send in a one page query letter first describing the project. A brief that appears on the rear cover of a book should be kept in mind when the query is submitted. Keep in mind that the correct font to be used in your book is "courier new 12 pt" with double spacing in the manuscript. The query letter may be made out in the same font, but without the double spacing.
Self Publishing
This form of publishing is far easier than the former. One can publish one's work at lulu (dot) com for free. A small commission is charged on the sale of the book. The best thing about self publishing is that you set your own price and age is not a barrier. From editing to formatting, everything is in your hands. The services provided by lulu would, of course, raise costs if you are interested in the international market as well. Lulu also provides templates for formatting, which you can get a friend, teacher or parent to help with. Although you need to plan the book cover yourself, lulu will help with that. Publishing your own book that becomes far easier.
One of the other ways of publishing is ebooks, which are becoming more and more popular these days. It makes possible instant access to your book via the internet.
Marketing of your book begins even before printing. The right market should be identified. You must also know where you want your book to reach. Your objective in publishing is what will determine the market.
Mistakes to Avoid
Your book must have mass appeal. You should choose a unique name for your self-publishing company to avoid a giveaway that it has been self-published. Be careful, because some publishers get heavy on print costs.
Help of professionals is necessary for selecting a title for your book, and for designing the cover. Do not paste a photograph of yourself on the front cover (unless you are a celebrity), because that is a definite giveaway that the book is self-published. You may paste it on the lower back cover.
The foreword could be left to those who will buy the book in bulk. The proof reading is one of the most important steps which again should be left to a professional. If these can be taken care of there is no doubt you will successfully sell many books.