Which resolv.conf file?

[Bob Bernstein]

I want to make a change or two to resolv.conf, but every time I 
come across it I flee in terror, warned that my changes will be 
destroyed and the linux gods angered.

What is the approved method for changing the list of DNS servers 
called upon by, in my case, Stretch on amd-64?

(Is there someone I could slide a few simoleons to in order to 
facilitate this business?)

Thank you

--
These are not the droids you are looking for.