Practical answer here: Overall, the aim is to not prevent someone from doing something, so you're actually checking with everyone if it's OK to use a space for Purpose X. If a subset want to use it for Purpose Y, they have a meeting with a facilitator. The facilitator does the hard work (there are guides) but overall people just talk about their interests and what they want to achieve. Basically everyone talks until there's an agreement in place, and this must be unanimous (otherwise people keep talking).
Here's an example video of a meeting in action, though the aim is there not to make decisions.
Boo. This is the left version of the attack helicopter meme.