Determine what the reference letter will be used for. If you are writing a letter for a Ph.D. program, ask the applicant for the program's guidelines and information about what he will be studying. If the letter will be used by someone who has finished a Ph.D. program and is searching for jobs, talk with the person about the type of work he hopes to do. If the letter is for a specific job, ask for a description of the job.
Ask for the name and address of the person who will receive the letter. Make sure you also get correct spellings and gender for any androgynous names.
Make a list, using a pencil and paper, of the qualities needed for the job or Ph.D. program. Your list should include the main job duties or points of the program. Do not focus on minutiae, but instead on the big picture.
Read over the applicant's resume or curriculum vitae. You should be familiar with the applicant's academic experience and past work experience. If you have questions, ask the applicant. You want to sound knowledgeable about the applicant in the letter. Incorrect information will reflect badly on both you and the applicant.
Make a list of qualities the applicant has that will make him successful in the job or Ph,D. program. Use the list you made of qualities the job or program requires and attempt, as much as possible, to match the applicant's qualities to the job or program qualities.
Pick two or three of the quality matches from your second list that you feel are strongest. Come up with a concrete example that demonstrates this skill in the applicant. For example, if the job called for research skills and you feel the applicant has those, list a time when you personally experienced the applicant working on a research project. The examples will give your letter more depth and it will have more of an impact on the letter's readers.
Write the letter. The final copy of the reference letter should be typed, but you can write the first draft with pencil and paper, if you prefer. The letter should follow a basic business letter format with names and addresses at the top. The first paragraph should be an introduction of you and your relationship to the applicant. In the second paragraph, give your general impression of the applicant. The next two to three paragraphs should focus on the qualities of the applicant that you matched to the job in step five. Each paragraph should focus on one quality and should include the examples you wrote down in the previous step. Conclude the letter with a paragraph about the ways you think the applicant will contribute to a job or academic program. The final paragraph should be a last pitch for the applicant and should include an offer to talk further about the applicant. At the end of your letter, leave several lines for your signature and then type your name. Include your contact information below the signature.