Mark Montgomery gives great advice for high school students on how to get letters of recommendation for college. Much of his advice would also work for college students wanting letters from faculty in order to apply for grad school or to get a job. Some tips include:
Establish a Relationship with Your Teachers: Well before you decide which teacher will write your LOR, you need to consider that a teacher will not know you very well unless you make an effort to get to know the teacher. Participate in class. Ask questions. Work hard. Go above and beyond what is required, to demonstrate your interest, your fortitude, your proficiency. Show up before or after school to ask questions, shoot the breeze, or comment about the course content. Express interest not only in the class, but in the teacher. Obviously, you will get along better with some teachers than with others. So focus your efforts on developing relationships with the teachers with whom you share some connection, some affinity.
Consider the Timing of Your Request for an LOR: Teachers are busy people. Don’t wait until the last moment to request an LOR. Don’t ask right after your midterm or final exam—when they are still grading stacks of papers...Look at your own deadlines...and consider requesting the LOR at least a couple of months before the deadline. Be considerate and respectful.
Pop the Question: When you meet with your teacher to request an LOR, you will likely be nervous. Try not to worry. Teachers field these requests all the time, and they expect to be asked...Don’t make the request via email or over the telephone. Do it in person: it makes a better impression. Your question can go something likes this: “Ms. Baker, out of all my classes, I have enjoyed yours the most. I feel that I’ve learned a lot from you. I like the material we are learning, and I think you’re a great teacher. I also think you bring out the best in me. I would like to ask whether you would be willing to write a strong letter of recommendation for me ... Of all my teachers, I think you know me best, and I’d be pleased if you would write my recommendation.” You want to be complimentary of the teacher, but you also want to convey a sense of pride in the work you have done in the class. Brown-nosing won’t work. But if you have built a good relationship with this teacher, he or she will be delighted to give you an enthusiastic “yes,” if you craft your request in this way.
Provide Your Teacher With Adequate Information: After your teacher answers an enthusiastic “yes!” to your request, you should present him with a slim folder with everything the teacher needs to fulfill your request. The folder will contain a variety of documents [such as resume, where to send letter, note of thanks] that will help him in writing a detailed letter filled with anecdotes about your skills and abilities. Presenting this folder immediately will convey how seriously you take the teacher—and the recommendation.
I always ask my students to give me a short list of what they perceive to be their strengths and weaknesses so that I can use this information (assuming I agree) to write a persuasive letter.