Find out from the guidance office how this process works at your school. Some schools submit recommendations from your file directly to the college; others request that teachers send letters of recommendation directly to colleges. You will want to get any necessary forms from the guidance office that a teacher may need.
Choose a teacher who knows you well. Specific information about your growth over the years, your strengths or some personal stories makes a better letter. Only a teacher who knows you well can point these things out. Ideally, you will have established a relationship with at least one teacher in high school by participating and working hard in class.
Select a teacher in your core discipline. Although it is good to list and possibly get recommendations from teachers in extracurricular classes or clubs, it is essential to have a recommendation from a teacher in at least one core class such as math, English, science or social studies.
Pick a good time to ask your teacher. Find out the deadline for submitting your college application, and ask for your letter of recommendation at least two months before that. Do not wait until the last minute and rush your teacher. Do not ask after a midterm or final examination, when your teacher will be busy grading. In addition, do not ask during vacation.
Ask your teacher for the letter in person rather than by email. If you are nervous, take some deep relaxation breaths before going in. Teachers are accustomed to students asking them to write these letters, so there is no need to be nervous. Ask your teacher during her off period or after class. Asking in person makes a much more positive impression than asking by email. You will be likely to get a better letter as a result.
Be prepared with a folder to hand to your teacher. In it, have a mission statement that you have written about what types of colleges you are applying to and why, a list of the colleges you are applying to, the form your teacher may need to use, an envelope for each college (stamped and addressed if the teacher is to mail directly), your contact information and a thank-you note.
Get the right number of recommendations. Too many letters will bog down your application. You are looking for quality, not necessarily quantity. Two letters from teachers and one from a counselor is a good goal.