"Stand up for yourself" = Don't let other people tell you what to do, how to act, or treat you unfairly. For example: "That guy was yelling at you for no reason! Why didn't you stand up for yourself?"

"Pick your battles wisely," or "Choose your battles" = Figure out what kind of things you really care about, and only fight for those things. For example, if your friend is never paying back money that you lend him, and he is also always whistling when he is around you (and you hate both of those things!), you are more likely to tell him to pay you back and just forget about the whistling. You are choosing your battles because you realize that whistling is no big deal, but paying back your money is a big deal.

"Roll your eyes" = A gesture that a person performs when they can't stand something. Very common in the US, especially among teenagers with attitude. Here is an example: http://gph.is/2n806s2 . Rolling your eyes is used to express exasperation.