You should begin to set yourself up for letters of recommendation early in your undergraduate career. Develop solid relationships with your college adviser and professors that you respect.
Carefully choose the people who will be providing the references and approach them in a professional manner.
If you are applying to graduate school a few years after graduating from college, you’ll want to make contact with old professors. Email them and tell them about your plans and see if they would be able to provide a good letter after years of not working with you. In these cases, you may want to provide one letter from a professional colleague or adviser who can account for your work ethic and style. Understand that admissions committees are looking for very specific letters that are best provided by academic professionals.
Recommendation forms have a box to check and sign that indicates your right to see the letter. Always waive your rights. Referees will feel more comfortable writing confidential letters, while admissions committees will give letters more weight when they have been written confidentially.
Give your people plenty of time. This shows them how prepared you are and demonstrates a respect for their time. Between one and six months is preferable; the more time the better. Two weeks is absolutely unacceptable.
Follow up with your professors, but don’t hassle. Check in when the deadline is near to see if the recommendation has been sent or if they need anything else from you. Ultimately, you are responsible for the letter arriving on time, so be diligent.
Formally thank your referees for their time. Professors are often writing several letters at one time and the thought and time it takes to write a good letter is time consuming. Show your appreciation and respect with a carefully handwritten note.
Report the status of your application, where you’ve been accepted and where you plan on going. You were a student of theirs and they want to know what you’re up to.