Im Flying By My Self And im 15 Any Suggestions?? Im REALLY Scared Because i Have to Switch Planes.?

Okay Im Going from Florida To Missouri BUT i Have To Witch Planes in Georgia & Im a FIRST time Fly-Er. What Should i Bring? Where Should i Sit On The Plane? What Can i have In My Carry-on? Do i Leave My Luggage At The FIRST Airport && Pick it Up At The LAST Airport? Or Do i have To Move It When i get to Georgia? i Just Need Some Tips && Advice Please!! #So'SCARED. :|