Writing letters of recommendation is generally part of a faculty member's job. Students need these letters to get into graduate schools. Indeed, grad school admissions committees generally won't accept applications that lack these important letters because they reflect the professor or faculty member's assessment of a student applicant.
Students need not feel powerless in the process because they do, indeed, have a great deal of influence over the letters that faculty members write. While professors rely on a student's academic history in writing letters of recommendation, the past isn't all that matters. Professors' impressions of you are important too - and impressions constantly change based on your behavior.
There are things you should avoid to ensure that the professors you approach for letters see you in a positive light. To avoid problems, don't:
Misinterpret a Faculty Member's Response
You've asked a faculty member to write you a letter of recommendation. Carefully interpret his response. Often faculty members provide subtle cues that indicate how supportive a letter they will write. Not all letters of recommendation are helpful. In fact, a lukewarm or somewhat neutral letter will do more harm than good.
Virtually all letters that graduate admissions committee members read are very positive, usually providing glowing praise for the applicant. However, a letter that is simply good- when compared with extraordinarily positive letters - is actually harmful to your application. Ask faculty members if they can provide you with a helpful letter of recommendation rather than simply a letter.
Push for a Positive Response
Sometimes a faculty member will decline your request for a letter of recommendation outright. Accept that. She is doing you a favor because the resulting letter would not help your application and instead would hinder your efforts.
Wait Until the Last Minute
Faculty members are busy with teaching, service work, and research. They advise multiple students and likely are writing many letters for other students. Give them enough notice so that they can take the time required to write a letter that will get you accepted into graduate school.
Approach a faculty member when he has the time to discuss it with you and consider it without time pressure. Don't ask immediately before or after class. Don't ask in a hallway. Instead, visit during the professor's office hours, the times intended for interaction with students. It often is helpful to send an email requesting an appointment and explaining the purpose of the meeting.
Provide Unorganized or Inaccurate Documentation
Have your application materials with you when you request your letter. Or follow up within a couple of days. Provide your documentation all at once. Don't offer a curriculum vitae one day, and a transcript on another.
Anything you provide the professor must be free of errors and must be neat. These documents represent you and are an indicator of how serious you view this process as well as the quality of work you will do in grad school. Don't make a professor have to ask you for basic documentation.
Forget Submission Materials
Include program-specific application sheets and documents, including websites to which faculty submit letters. Don't forget to include login information. Don't make faculty ask for this material. Don't let a professor sit down to write your letter and find that she does not have all of the information. Alternatively, don't let a professor try to submit your letter online and find that she doesn't have the login info.
Rush the Professor.
A friendly reminder sent a week or two before the deadline is helpful; however, don't rush the professor or offer multiple reminders.
Forget to Express Appreciation
Your professor took the time to write for you - at minimum an hour of his time - so take the time to thank him, either verbally, or by sending a thank you letter or note. Remember that you want your letter writers to be in a good mood when they write your recommendation and to feel good about you and their decision to support your application to graduate school.
Write a thank you note to your recommender and when you ask for another letter in the future (and you will - either for another graduate school program or even a job), the faculty member will be much more likely to write you another helpful and positive recommendation letter.