What's Expected of an Alliance?

First off, not the game's alliance community. I mean a community alliance creating an alliance with another community alliance.

So I looked but couldn't find a post like this, maybe I missed it.

I'm an alliance leader, but honestly, I'm not good at this game. I'm still learning and we're not a strong community alliance. When making an alliance with another community alliance, what's expected from both parties? And I know it'll probably vary between each one. But what do you expect or ask for?