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.

Why students checking facebook on class are regarded disrespectful, while a professor who checks his facebook on a symposium as another professor is reading his paper is said to be cute and cool? Are there absolute boundaries between righteous and evil, right and wrong?

These are two very different questions-- First, I would not regard the Facebook checking prof as cool. Going on to your computer while someone is giving a seminar or talk is just disrespectful. I doubt our Facebook checking prof would take kindly to someone doing the same to her as she delivered a talk that she had been working on for months. As for your other monumental question, I would suggest that while there are some acts that are clearly always wrong, there are many that might be wrong in one context and not so in another. Lying is generally wrong but if you are doing it to save an innocent life or lives? The term "boundary" is of course a metaphor that would need to be unpacked to answer your question but on the face of it (another metaphor) I don't think there is an absolute boundary between right and wrong such that we can say of every act- this one is on the righteous side- this evil. Thanks