There are various types of letters of intents for instance if you are applying for university or college then you would need to create a letter of intent for graduate school or university. If you are planning to apply for a job then you would need a letter of intent for a particular job position.
At the end you should sign off with "sincerely yours" or any other related salutation. If you are applying for a particular job then you need to create letter of intent that contains the following. First of all mention your name, address and contact number.