When are flight tracks publicly available?
Skimming FlightAware's FAQs:


The most consistent way to show up on FlightAware is to have your flight worked by ATC (a squawk code and an IFR flight plan), or to fly an airplane equipped with ADS-B Out.
FlightAware doesn't really track VFR flights unless they have ADS-B Out:


  some VFR aircraft with flight following are available on the position maps but it largely unreliable
  
  You can block your tail number in a few ways. Both the FAA and FlightAware operate block lists.