1. Think of people who you have come to know over the years who would be able to comment on your positive qualities. Choose someone who is in a position with some responsibility. (A reference letter written by an individual who has some status by virtue of the position they hold is often better than one written by a best friend.)

2. Remember that you are asking someone to take some time to do a special favor for you.

3. When you make your request, begin by explaining what you are attempting to do and invite them to help out by writing a reference letter. If the person writing the letter has some idea about what you are applying for, they will be able to frame their comments in a way that lends itself to the application. 

4. Be sure to provide the person with some general background and reminders of things that you have done. Remember that people in positions with some degree of responsibility are generally busy do not have a great deal of free time. Make it as easy as possible for them by providing as much information as possible.

5. If possible, include the name of the institution you are applying to and the type of course, or the name of the employer and the job description.

When you call to ask for a reference letter:  
What do I say? (Write it down before you call.) Download this script for a sample (pdf / rtf ).

Be polite, courteous and keep in mind that you are asking for a favor. Remember that a reference letter is not always an easy thing to write.
Provide some background information that you feel may be helpful. The person writing the reference letter will then be able write the letter based on the job you are applying for.

Often the people that tend be asked for reference letters are very busy, and will need time to sit down and write the letter.

Give them plenty of advance notice.

Let them know when you need the letter and exactly what it is for.