Setting debug-on-error and debug-ignored-errors

[carlmarcos]

Does one usually set debug-on-error and debug-ignored-errors variables before 
launching emacs.

I am also having difficulty seeing the errors

For instance, suppose I remove an opening  parenthesis, to get the error 

Invalid read syntax: )

Why does emacs not help me by also showing me the file and line number at which 
it is complaining.
I usually have a number of init files that are run from my .emacs file, yet 
emacs debug errors does not print such details.