Move to Los Angeles. Though some TV sitcoms shoot in New York, the majority of production offices are located in Los Angeles.
Hone your comedy writing skills. Enroll in a writing class at a film program such as the University of California Los Angeles Extension class, Comedy Writing for All Mediums. Classes and workshops help refine your comedy writing skills and teach you the ins and out of the business side of a writing career.
Write two half-hour comedy scripts, one original and one of an existing TV sitcom that's still on the air. The original sitcom script shows your creativity and provides a sample of your "voice," that special way you put words and images together that sets you apart from all other writers. The existing TV sitcom script demonstrates how well you can write in the "voice" of an existing show, which is advantageous when you interview for a staff writing position.
Choose an existing show that's been on the air only one or two seasons and is moderately successful and critically acclaimed. If you choose a popular, long-running sitcom, chances are thousands of other writers are writing the same show, which means the market is saturated with these samples, making it harder for yours to get noticed.
Polish the two scripts until they are as good and funny as you can make them. Because these scripts are your calling card, they have to be the strongest example of your work. You may write a dozen other scripts, but the two you choose as your samples have to meet a high standard. They must be humorous, heartfelt and distinct. Revise the scripts in a class setting, or join a writer's group to obtain feedback on the comedy and structure of your work.
Buy a copy of an agency reference resource that lists the contact information and employees of every small, medium and large talent agency in Los Angeles. Visit a bookstore and browse the film section to find these resources, or ask a member of the bookstore staff to direct you to the appropriate section.
Make a list of 20 talent agents and send them query letters, which provide an attention-grabbing synopsis of your scripts and request that the agent read your work for possible representation. You cannot get an interview to write for a TV sitcom without having an agent represent you. TV sitcom showrunners will not read unsolicited material for legal reasons, and because unrepresented writers have not been vetted by someone they know and trust.
Follow up two weeks after sending the letters with calls to the assistants of the agents whom you queried. Be friendly and courteous and ask the assistant if he is willing to read your work. Many agents are too busy to read the work of a new writer unless a talent manager or an assistant recommends the writer's work.
Find internships on TV comedy shows, or apply for jobs as a production assistant or PA on a TV sitcom production. Internships provide direct access to producers and creators of TV sitcoms, which gives you the opportunity to network and get your script read. Make friends with anyone on the writing staff or an assistant to a writer who is willing to read your material and give you feedback. Though a PA job is less than glamorous and entails long hours and low pay, you get to see the production of a sitcom and meet those responsible for putting on the show. Sites such as Entertainment Careers, Hollywood Entertainment Jobs and Film Crew Pro, provide internship and PA jobs information.
Strategize. Once you've obtained representation, target the sitcoms that fit your sensibilities and that have slots open for staffing. Your agent will submit your samples to the showrunner and producers of the shows you target and sell you as a unique addition to the writing team. If your sample is strong enough to stand out, you will likely be called in to meet the showrunner of the sitcom.