Most selective colleges ask their applicants to submit two recommendations from teachers. These can have an important bearing on your chances - particularly if they are negative.
Teachers have too much to do as it is.
Writing recommendations takes a lot of time, especially if you attend a big school and the teachers you ask are popular. Give your recommenders plenty of time. More College Prep Standardized Tests Applying Financial Aid Visiting College College Downloads College Planning Newsletter Make It Easy for Them. When you ask teachers to write recommendations for you, give them everything they need, including your application deadline and a stamped, addressed envelope. Some guidance counselors and books recommend that you also give your recommenders a list of your activities, to remind them what you've been up to the last few years.