<p>Don't sweat -- just lay the ground work. Say:"You've been a great instructor and I feel I've been able to excel in your class. Some of the schools I'm considering next year require teacher recs. Can I ask if you'd consider writing one for me in the fall? I'll provide you with the forms and schools as I narrow them down. I'd love to sit down sometime to answer any questions you have about me too."</p>
<p>Most likely, your teacher is experienced in writing recs and hopefully will be able to recount good anecdotes about your personality, abilities and intellect. In your "sit down" with him/her, highlight these and maybe offer examples that you can recall.</p>
<p>All colleges that ask for teacher recs have a form for them to fill out as well as open space for them to write text.</p>
<p>its better to give the recommendation to your teacher before the summer vacation, since it gives that teacher ample time to write it, but ask it in a nice way, "Oh, _____ class was my favorite class in my ________ year, I just wanted to know if you would like to write a college recommendation for me." After your teacher writes a recommendation for you, be sure to give that teacher a "thank you" card to show your appreciation for him/her.</p>
<p>I second AznN3rd. The last day of school is not the time to ask teachers. Don't sweat it. They'll still be there in the fall for you to ask them.</p>
<p>Though I too have heard the rule that you should tell your recommenders at the end of your junior year, I personally didn't; I'm waiting until next year, when they'll have a month and a half to do my recommendations, which is ample time.</p>