Read the RFP (request for proposals) or other submission instructions carefully to learn specific guidelines regarding the letter of intent. For example, most federal grant applications are extremely specific in terms of file size, format, naming conventions, supporting documents, etc.
Determine the type of information required and the LOI deadline.
Outline the info required for the letter of intent. Although it will vary depending on specific guidelines, the information required will typically include the name, affiliation and credentials of the principal investigator or project head; the name, credentials and affiliation of key research personnel; brief bios (biosketches) of researchers involved; participating institutions; and a name and summary of the proposed research project.
Write the summary of your research project for the LOI. Be specific in regards to the research objective, the methodology, the expected outcome, the benefit gained, populations to be studied, human subject parameters (if any) and your project's funding requirements. Include info on any past research studies that are relevant to the proposed work. Be sure to emphasize any similar research literature that features the principal investigator or key personnel.
Solicit the input of key collaborators regarding the research plan.
Collect the bios of key personnel and any other documentation that needs to accompany the letter of intent.
Submit the letter of intent before the deadline, and after it and all supporting documents have been proofed and assembled in the required format. Most grant application materials, including LOIs, are submitted online.