I am going to California by myself for the first time I am nervous I would love to hear your ideas please!!!!?

Heey I am 15 and I am travelling for the first time to California , unfourtenetly its not a dierect flight since I live in Canada :( . Since I travell on a plane at least twice a year I do not need a flight attendant , Do I need a letter from my parents saying I am allowed to fly. My parents have only talked to me about how to stay calm when I am on the plane by myself. What would I need for customs. Also what would you suggest I wear on the plane , I am bringing my snuggie on the plane to keep me warm. Also what activites would you suggest to do on the plane I am going into grade 10 btw and I have excellent marks but I want to make them greater , also since it is summer I probally un available to get my hands on any text books! Dang I sound like a nerd. So OH and i am leaving on tuesday and I know what you are going to say , How about you ask your mom or your travel agent , I just want to see If it is actually worth the time asking them. Please answer I will like all of your awnsers :)