Fidonet and Usenet were good places to ask.
Looking at the source code of open source projects, especially when some piece of the code was doing something that you wanted to figure out.
There were actually quite a few resources before StackOverflow.
Truly, a dark time compared to the more enlightened "cut and paste from some website solves all problems" utopia we now live in.
Tribal knowledge and becoming a ninja at debugging and reverse engineering ancient code seems to do the trick.
I’ve lost weeks of my life fighting bugs in IE 6.