Follow standard procedures in obtaining references, and use conventional formats in writing letters of recommendation.
References are an essential component of almost all admissions, grant, and employment processes. Managers and other individuals in any selection process need evaluations from individuals who have had long and close contact with applicants in order to assess accurately their abilities and accomplishments. The number of recommendations required by employers and universities usually ranges from one to five, with three being the most common number.
There are two basic forms of references: oral and written. Most often, oral references are conducted by telephone. The name, professional title and affiliation, address, and phone number of each reference are included in a list of references, which is often mentioned in résumés and application letters but always kept separate from them.
Give your list of references to a potential employer or to a selection committee only when it is requested. Your recommenders are doing you a favor. If you subject them to too many intrusions, you may find them less willing to help you in the future.
Written letters of recommendation are more formal. Often, they are written to a specific individual for a specific position. In other cases, however, letters of recommendation are written for a general type of job or for graduate school and are included in a collection of letters of recommendation called a dossier.
See Obtaining References and Letters of Recommendation for guidelines in developing a list of references and obtaining letters of recommendation.
For guidelines on writing letters of recommendation, see Writing Letters of Recommendation.