How To Know When You Need To Shave?

My friend asked me if i shaved because she sed there was hair on my legs. I have bad eyesight and from my point of view its hard to see. I asked my mom and she says she doesn't see anything but my friend says i need too. I shaved before but how do you know when and where to shave?!? I dont wanna shave hair you cant see because it will grow back thicker but i dont wanna walk around with all this hair on my legs.... I CANT TELLL HELPPPPP