Why is piggy so obsessed about finding the others and calling a meeting? What does this say about his character and personality?

I'm not sure what section of the text you are referring to, but Piggy is a master of organization. He has a unique ability for problem solving and putting things together. At the start of the novel, Piggy is anxious to use the conch is order to assemble the survivors, count them, and learn their names. He understands that without knowing who you have..... you won't know who've you've lost. His intent is to create a kind of order amongst the boys.