In general, you should only ask those people who know you well. For the most part, this includes your teachers, professors and work supervisors. For graduate and professional school, the recipient is most interested in your academic performance as an undergraduate and your ability to think critically. For job recommendations, intellectual ability and creativity are important as well as past accomplishments in previous positions. So tailor your requests to target the appropriate letter writer, one who knows you best with regards to the requirements of the position that you seek.
Use your best manners when making your requests. Say please and thank-you. Do not simply leave a note for someone demanding that you need a letter by the end of the week. Personally, I would completely ignore that type of request. Remember, you are asking someone for a favor so be pleasant and respectful. After all, those are personality traits that a letter writer is likely to include in your reference. Also, beware of modern journalistic pitfalls when submitting a request in writing, including email. Write complete sentences that are grammatically correct; pay attention to spelling and capital letters and avoid fad phrases or abbreviations. Consider your request to be an opportunity to remind the letter writer of your adroit communication ability. Your initial contact should be in person, if possible, or by phone call. An email request is fine if you have relocated from the area or if repeated attempts to make contact have failed.
You must understand that regardless of what I think about you personally, I can only write letters based on what I observe. If you earned a low B or C in my courses, I am limited to those results. Your low grades will be reflected in my comments about your intellectual capability, performance and critical thinking. If you did not earn at least a C in my courses, I question the reason why you would even ask me for a recommendation. You may want to consider asking for a letter from someone who has seen you at your best, even if that person does not know you as well as I do.
Generally, you are asked whether or not you waive your right to examine letters of reference. My impression is that a letter carries more credibility if the student waives this right.
Please understand that regardless of how important this letter is to you, it is not my priority. That is not to say that I do not care about you, but I must budget my time if you expect an honest, effective letter written on your behalf. Therefore, if you plan to request a letter of recommendation from me, please make sure that I have the following information. I will not bother to write a letter for anyone unless that person takes the time to start the process.
Here is what I require before I will start composing your letter:
Make a checklist for items 1- 7 so that you save time for both of us. If I have to contact you for these items, that will only add to the delay.
Please let me know how your situation develops. Did you get the job? Did you get accepted to graduate school or successfully transfer to another institution? I like to know if my efforts are helpful to my students and I enjoy being a small part of other people’s lives, especially former students. Staying in touch with my former students is one of the most valued perquisites of my profession. I can also use your success to measure the effectiveness of the letters that I write on behalf other students.