Ask the teachers who know you the best
Often students make the mistake of asking the teacher who gave them the highest grade for a recommendation letter. That teacher may not really know you very well, on a personal level, and be at a loss as to how to describe you and your best qualities. Sometimes, it is in the classes where you might have really struggled, but still achieved success that would make for a stronger recommendation letter. Especially if you have earned the teacher's respect for what you overcame. Also, if one of your teacher serves as an adviser to an extra-curricular activity that you have become seriously committed to- that teacher knows you now in a different light and could comment on additional skills and /or passions. Whomever you do decide to ask- please ensure that they actually do like you!