What is the best way to answer questions and teach people on this forum?

Except for the last one, those are all runtime errors. I mean, i see topics with names like

exit status 1
'LED' was not declared in this scope

or

expected constructor, destructor, or type conversion before ';' token

etc.
i was thinking more of a list of that sort of manner, with explanation on what that actually means and what may be the cause, and how to solve it.
Your list can be useful, but i would break it up into several parts.

  • Anything to do with Serial
  • Explanation about loops and it's pitfalls.
  • variables and their use and scope. Including how computations are handled.

It is of course an issue that in many cases, responders refer to the reference, when the OP obviously hasn't.