Copyright any songs you plan on submitting. This will safeguard you from people using your songs illegally and without your permission.
Publish and register your songs. Contact a performing rights organization like ASCAP or BMI. This will make it easier down the line to ensure you of any royalties you should receive. Work with professionals in the business. Align yourself with people who can represent your song as a viable product. Hire a manager and/or a lawyer. The main reason for doing so is that a reputable manager lends you and your songs credibility. Your manager or lawyer can help you get a publishing deal. Publishers are companies that can market your songs. They are gatekeepers and license music copyrights for use in movies.
Network. On top of getting to know players in the music industry, work your way into the minds of people in the movie industry, like directors, producers or actors. Lisa Loeb lived across the street from actor Ethan Hawke. She gave him a tape of her song "Stay (I Missed You"), who gave it to Ben Stiller, the director of "Reality Bites." He put the song into the end credits of the movie, it was included on the soundtrack and became a huge radio hit. The chances of this happening to you are slim, but it can't hurt to try and make these connections.
Get to know music supervisors. They oversee all musical aspects in a movie, including the soundtrack. Look them up and contact them if possible. Ask them if there is anything in particular they are looking for.
Send the music supervisor a CD with all of your contact information on the CD and in the jewel case. Include information about the songwriter, artist, publisher (if any) and other vital information. Include information specific to the songs, such as genre and tempo and for which project you are submitting. Be sure to research what type of music a music supervisor is looking for before submitting. Your death metal song might not fit in their romantic comedy.