Just like a cover letter, the letter of intent discusses your qualifications; the difference is that instead of applying for a job, you are explaining why you are a good candidate for the degree program. Begin by giving an overview of your undergraduate education and what aspects of that education make you ready for a graduate degree program. Highlight important experiences such as hands-on training, a study abroad program, volunteer experience or job experience. Entrance into most graduate programs is competitive, so sell the graduate coordinator on your experience.
The graduate coordinator will want to hear about your rationale for seeking an advanced degree. Be positive and discuss your desire for the degree in terms of your love for the field and what you hope to do with your degree once you have graduated. Students need to have a passion for what they do to get through the master's degree and thesis or the Ph.D. program and dissertation, or they will drop out. Explain why you have the drive and desire to get through the program.
Explain specifically why you selected this school. The graduate coordinator will want to know what this program can do for you; for example, if you are interested in cross-cultural psychology and this school has a good cross-cultural psychology program and several noted researchers as faculty in the program, then explain that. If there are any particular staff members you would like to work with, identify them and discuss the connections between your interests and their research.
In the last section of your letter, thank the graduate coordinator for her time. Some graduate programs have interview processes and some do not; if yours does, politely request an interview. Provide your contact information, such as your telephone number and your email, in case the graduate coordinator needs to call you about your application. This information is probably already on a formal application or in their computer, but putting it on the letter is polite because it spares them the trouble of having to look it up.