Take advantage of every opportunity to gain experience. Volunteer your services for student film projects and local television programs. Regard these efforts as part of an apprenticeship or training process. You will acquire valuable experience in working with television and film media such as matching musical ideas with moving images, creating atmosphere with sound and working under the pressure of deadlines. This process will also allow you to make contacts and begin building a resume in the business. Student filmmakers become professional filmmakers.
Do your homework. Familiarize yourself with the important soundtracks and music composers. If a television program asks you for a "Twin Peaks"-like score, you will be prepared to deliver. Musical scores in television and films tend to be formulaic. Once a certain sound or style becomes popular, it used in a variety of different contexts.
Develop your own musical ideas and styles. This is the flip side of the coin. Although music scoring tends to be formulaic, directors and producers are curious to find something new. Ry Cooder's musical score for "Paris, Texas" broke new ground and Cooder quickly became very much in demand. Cooder's style has since been imitated by numerous composers for film and television. Develop your own ideas by composing various types of music.
Make a professional quality demo. The demo is a representation of the range and quality of your work. In addition to demonstrating interesting musical content and ideas, the sound quality should be professional as well. This requires booking time at a professional recording studio and hiring professional musicians and a recording engineer.
Publicize your work. Develop a website. Write a short bio about your musical background and experiences. Provide samples of your work that prospective employers can hear. Highlight the important points of your resume. In addition to the website, put together a promo package that includes your demo and contact information. Once you have had some success, begin contacting booking agents.