Develop a list of legitimate songwriting agents. Unethical people are out there ready to prey on songwriters. Check the library for an industry guide to agents. Make sure the agents you are contacting have an established record of success in supporting the careers of up-and-coming songwriters. Check the agency's client list to determine their previous track record.
Write a brief query letter detailing your songwriting experience and any other qualifications relevant to your pursuit of a songwriting career. Touch upon education, awards and performances that relate to your songwriting expertise. Disregard any agent who charges a fee simply for listening to your demo.
Package and send your materials. This includes your query letter, recorded demo and, if you're a performer, any publicity materials, like photographs and a bio. Some agencies may permit you to send these in digital form. Others may require hard copies of these materials. Inquire with the agency in question to determine which form of submission they prefer.
Follow up on your query. If you haven't heard from the agency after one month, send a polite email or make a phone call to make sure the materials were received and are being reviewed. If an agent responds by declining to represent you, ask whether he has any feedback or comments on how to increase your chances of representation. Keep trying. It's difficult to find representation as a songwriter, but success only comes to those who persist.