Textbooks - PHS photo IDs make the process of checking out textbooks go MUCH quicker (ID's can be purchased for $5 in the counseling office if you have lost yours)! 
Remember to
cover your books.  This helps keep them in decent shape.  Brown paper bags from grocery stores help the "wear and tear" the best but any covering helps.  You can use news paper, wrapping paper or butcher paper too!