User stories & feature development
One thing we avoid at Vanilla is doing "wishlist" features. That's where someone says "wouldn't it be great if I could do X" and that gets rolled into core or even becomes yet another addon without some critical thinking applied. That's the road to bloated software that's hard to use because it doesn't have an opinion. Great software means making informed decisions in the design process, and to do that, we need some concrete goals.
We've been talking about user stories as a vehicle for making sure we are fulfilling actual needs, not wishes. So when we starting thinking about adding a feature, a good starting place is collecting some user stories so we know what we're trying to accomplish and not designing in a vacuum.
To get involved in a our larger issues, feature discussions, and even our pull requests, thinking about the user stories we are trying to fulfill (and adding your own) is a great way to participate usefully in the feedback process.