For college recommendations, you must ask me in person and before the start of your senior year. There is a set number of college recs that I will write and it is on a first come, first served basis.
For summer programs, internships, etc, you must also ask in person and at least 3 weeks before the due date.
Keep in mind that I will be honest in my recommendations, so if you haven't been a positive influence in class or haven't worked hard, etc, that is what I will write. If you feel like I don't know you or your personality very well, then I may not be the best person to write your rec and it would be wise to ask another teacher.