Most colleges require the submission of one to three recommendation letters, written by teachers, coaches or other professionals that know you as a student. If you really want a teacher to put in a good word for you, a word of advice: ask early.
Teachers are happy to give out gold star recs (in most cases!) However, come November, teachers are swarmed by high school seniors who need to send off college applications and meet deadlines. If you’re asking for a letter of recommendation in the fall, you’ll probably get a somewhat specific but mainly “templated” response. The take-home – don’t ask in the fall.
The best time to ask for a letter of recommendation is the end of junior year. Approach your favorite teachers and let them know you’ll be filling out your applications and applying to this school and that, and would appreciate if they could write you a letter. As classes are still in session, you and your wonderfulness will be fresh in their minds, and they can easily write about this wonderfulness. Plus, they’ll have plenty of lazy summer days to really focus on writing that letter. More focus means more insightfulness means more gushing compliments to give you in the letter.
Aside from asking well in advance for recommendation, make it easy on your teachers! Have your forms filled out, your envelopes pre-addressed and pre-stamped, and a brief resume that highlights your strengths and extra-curriculars, ready to go!