Do you use an external flash? yes
if so, in what situation and will you use it and what technique? when it will improve the photo and isn't disallowed for some reason. I typically use it off-camera and have been known to mount it to the tripod instead of the camera. Or I'll use it on-camera with a Better Beamer. All decisions depend on the shot.
and what flash? AF360FGZ
if not, do what are your ways in dealing w/ low light? depends on what I'm photographing. I'd rather increase iso than use a shallower dof in most cases. Limited focus can be overdone and while it plays well on photo boards, it's not seen as "art" by most viewers.
Honestly it's like anything else in photography - you decide what you want to show, and do what it takes to show it. It's a tool, not rocket science.
The tools work flawlessly; training the photographer (me) is what's taken time and practice.