I took lessons in high school for about 3 1/2 years and had to stop since I don't plan on majoring in music in college. But I do plan on still playing in college in concert bands and I already got accepted in the marching band and would like to remain semi-competitive. It seems that many people discourage the use of some book without a teacher. Is there a certain way I should approach my practice now without professional instruction? My teacher made a it a point to go through most arban excersies to make sure I know what to do. I have plenty of other books such as clarke and a number of random etude books. Any thing else I should invest in?