<p>Am I supposed to somehow notify the colleges that I've been accepted to but have decided not to attend, that I'm not planning on attending? The answer might be really obvious but I don't know :/ What should I do?</p>
<p>If they included a yes/no type of reply postcard in the acceptance packet - use that. Otherwise, the courteous thing to do is simply e-mail the admissions department. Include your name and date of birth so that they can easily identify you. A very simple “Thank you for you offer of admission. I have decided to attend another university.” will suffice.</p>