Aside from reading, learning, and getting good grades. What are the best things an undergraduate in philosophy can do to make their prospects for getting into grad school better?
It depends in part on what field you want to go into but apart from studying for the GRE etc make sure to develop strong mentoring relationships with a professor or two. You will need strong and detailed references. Also, work diligently on your writing- which entails reading you work aloud with someone.