Best way to allow one plugin to use anothers functions

[mvlcek]

So from my understanding, in the plugin that is using the other plugins functions, I should create a function and put all references to the other plugins functions in it. Then call that function with the common hook.

Yes, when you encapsulate the calls to other plugins in your own functions, you can more easily add support for plugins with similar functionality. Of course, if you call this other plugin's function just once, this might just be overhead.

Just don't try to define a function, if it is not defined yet - it won't work consistently.