Listen to as much music as possible, both old and new, to gain insight into different genres of music and the quality of different sounds involved.
Get a degree in music production, if possible. While it isn't necessary, it can only increase your knowledge of music production and your list of contacts.
Get some experience. Try and get a job at a recording studio as an assistant or an apprentice in order to gain the first-hand knowledge you'll need to produce music and start climbing the ranks.
Start your own studio, whether it requires a six-figure investment or be as basic as a laptop, interface and microphone. Start recording as many artists as possible, offering your services for free to entice new clients. This way you can build up a portfolio, as well as increase your gear list as time goes on.
Network with people in the music industry. Tell your clients to tell their friends and fellow artists about your services. Go to shows and music industry seminars and conventions and talk to as many people as possible. Be sure to carry business cards and copies of your work, if possible.
Advertise your services. Build a website and include clips of your work. Plug your studio and services on social networking sites such as Facebook and MySpace, as well as in recording and other music forums. Put up fliers in local record stores. Buy ads in trade magazines.
Seek out marketable clients and hook them up with hit songs. Many modern music producers perform functions usually reserved for A&R (artists and repertoire) executives and managers. Cultivate the careers of marketable artists and involve yourself in getting them record and publishing deals. The more hit records you have under your belt, the more likely you'll bring in more clients of reputable quality.
Stay current. Music production technology and trends are always evolving. The same production techniques that sold hit records in the 1950s don't cut it today. Listen to modern records and educate yourself on new recording techniques and production styles.