Familiarize yourself with the role of a publisher. In a column published on the Berklee College of Music website in 2004, then vice president of A&R for Sony Music, Eric Beall advised that the job of a publisher is to place songs with other artists. Other responsibilities include looking for new writing talent, listening to demo tapes, placing songs on compilations and distributing songwriting royalties to the writer or writers.
Research intellectual property law. There's an old saying in the music industry: "Where's there's a hit, there's a writ." Many high-profile artists and songwriters have sued each other over the distribution of royalties and writing credit. By understanding intellectual property law, you'll be well-informed when you deal with songwriters in your capacity as their publisher. Every songwriting setup differs, but the law remains the same. Only the credited writers receive publishing royalties, regardless of who played on the record.
Study the end credits on films and television shows. Make your own database of the songs and writers that appear in the credits. These songs didn't get to television by accident; a publisher did a deal to get them there. Use the American Society of Composers, Authors and Publishers website to search for the song's publisher. Once you get 100 or so songs in your database, you'll be able to see which publishers have a good hit rate.
Find a suitable college course. Berklee College of Music is famous around the world for its music tuition. University of California, Los Angeles (UCLA), also runs a course in music publishing. Record labels typically have an L.A headquarters, so studying at UCLA may provide internship possibilities, too.
Intern with a music publisher. Browse the publisher directory on the Music Publishers Association website and a list of music publishing companies you like. Send your resume to each company, offering to work for free in return for training.