[mnemonik]

This is a great question, thanks for asking.

For crashes, definitely submitting the crash report found in about:crashes helps a ton.

Checking the browser console for an error message + stack and pasting that in a bug + description of bad behavior can be useful.

Finally, in extreme cases you can enable all the devtools logging[0] and then run firefox while piping stdout into a log file. This is a firehose of information, but it should hopefully point to the part of the code base that is misbehaving.

[0] https://wiki.mozilla.org/DevTools/Hacking#Enabling_DevTools_...