Search for the music publishers you think may be interested in publishing your work. A publisher of very commercial pop music, for example, will probably not be so keen on publishing a heavy rock song. The Music Publishers Directory (see Resources) is a good online guide to American, Canadian and British music publishers, and includes telephone numbers, websites and postal addresses. The "Music Publishers Registry" book is an even more detailed source, selling for $75 as of January 2011. Music magazines are another good source of information about music publishers.
Contact music publishers in a professional manner. Telephone or email a publishing company by way of an inquiry. Show some knowledge of the publishing company and what they publish. It will show that you are not just sending out your music to all and sundry, but that you are taking the time to pick out who you think will appreciate your music. Ask, politely, if they are looking for new material.
Make a demo of your music and have it copied onto CDs ready for mailing. A good-quality recording will give any publisher the sense that you are serious about your songs and music. A big production isn't necessary for a demo, as a good song, with a simple piano or guitar accompaniment, should be enough to impress a music publisher. Don't be arrogant or bombard a music publisher with too many of your songs. When you send your music, include a polite covering letter and ask for any suggestions as to how your music could be improved. Send any details of your experience in the music industry to accompany your music.
Describe your music, but only in one or two sentences. It's up to the music publisher to evaluate how good, or bad, your music is. Make gentle suggestions regarding the arrangement of your songs and music.