Over the past month I've noticed many questions - particularly in problem-players and gm-techniques - which are answered by suggesting that the GM have a session 0 (a pregame session where the ground rules of the campaign are laid out).

I feel that a community Q/A detailing resources, strategies, and topics of discussion that facilitate a productive session 0 would be of great benefit. When a session 0 is suggested, we could link to this question to help guide the asker in the right direction while they are tailoring a session 0 for their campaign.

The obvious problem with such a question is that it veers almost immediately into "primarily opinion-based" territory. Could it be asked in a way that is on topic, or is that impossible given our format?