How do I choose a teacher for my teacher recommendation letter?
It's always best to choose someone who really knows you, someone who has, perhaps, seen both your strengths and your weaknesses. Then, your teacher can attest to your strengths and maybe even write about times when you've overcome your weaknesses. If you choose someone who knows you on a superficial level just because you think they're considered to be the best teacher at your school, then you might not get the same in-depth recommendation letter that someone who knows you well can write.
Another possible way to go about choosing is to ask someone who teaches in the field that you're interested in pursuing. For example, if you're interested in math, having a math teacher talk about your passion for the subject and give concrete examples can be very helpful to your application.
Typically, colleges also want more recent teachers, as opposed to someone who taught you freshman year. Asking a recent teacher allows colleges to see a more up-to-date image of you.