The easiest way to view sample Letters of Intent is by logging on to Google images and entering "Letter of Intent" in the search prompt. Browse through all of the Letters of Intent and print up a few for future reference.
Observe the format and structure a well made Letter of Intent is organized.
You can find Letter of Intent Templates by logging on to websites such as docstoc.com. Upon finding a template, simply download it, and follow the templates instructions on how to fill it in.
Head down to your local library and find the career resource section. Just about every library has such a section. Here you will find books on Business Plans, Business Proposal letters, Letters of Intent (with samples),
If you are writing a Letter of Intent for a College, request a sample letter of intent from your High School guidance counselor or in a College resource center within your city.
Refer to my resources section for a short list of more websites that offer Letter of Intent samples and instructions.