For US schools, teacher and counselor recommendations highlight different aspects of you, the student.
For UK schools, the reference written by the counselor combines these roles.

adapted from an experienced admissions officer in the US: 
A good deal of the reading of student applications is like theatrical lighting. The students are out front on center stage for a few months while the applications are being read, and each student's job is to turn on all the lights that apply. Some lights flood the whole stage, while other lights spotlight a particular angle of an actor.

The teacher recommendation is a spotlight, focusing on particular skills in the class(es) in which the teacher has taught the student, in order to establish your credibility in the college classroom. Teachers do not need a resume: they only need to describe you in the world in which they know you. Schools are interested in their judgment (and the personal observations on which that judgment is based) of your capabilities and traits. When the teacher is a coach or adviser with insights into leadership, maturity, commitment, colleges welcome these comments. 

Teachers can only tell the story of the you they've seen in class and around school if you ask them well in advance of deadlines to give them to time to write clearly and well. So when do your schools need those recommendations? What day is today? Why not ask those teachers right now? How many teacher recommendations do your colleges need? Do they need recommendations from specific teachers? Find out what YOUR colleges want and when they want it.

Use teachers from junior year or a current teacher (if they have known you long enough to write credibly). All the better if you get a recommendation from a classroom teacher who has also been involved with you outside the classroom, but unless a college specifically requests it, don’t use a coach or someone who cannot speak to your academic achievements and potential.

Think about who knows your strengths. That may be a teacher in whose class you’ve gotten top grades, but it could also be a teacher who knows how hard you’ve worked to get B’s and C’s. If you need a recommendation from a non-academic person, request one from someone who knows you well: a coach, employer, adult co-worker, religious or youth-group leader, or an adult in the community with whom you have had regular and positive contact.

Remember, the teacher  is doing you a favor. Make sure to give them at least one month before letters are due, but, as with anything, the sooner the better. Many teachers like to have July to write recommendations, so if you ask them in May or June of junior year, you’re doing great. (If the teacher is leaving UAS, get the letter before they leave!) Remember, the deadline is the last possible day the letter/application may be received by the admissions or scholarship committee, not the day you put it in the mail: set your own deadline at least one week before you need to mail your application letter.

Talk to your recommendation writers about what you remember about their class and your participation in it. Highlight a particular incident, paper or anything else that might help them provide anecdotal information and specific examples of your achievement, rather than just vague praise.

Write a brief thank-you note to the writer.