My workplace is currently just starting out with a UX group, and we are currently working on guidelines to standardise components, patterns, tools etc used across all our products. So my suggestions is that you actually need to get everyone in one room for a workshop.
The things you need to nail down:
- The design process that you generally follow (keeping in mind that it can change depending on the project).
- The tools and outputs, and design decisions behind the output. If you don't record the design decisions you can end up coming back to a design and not knowing why it was done in a certain way. So figuring out how this is captured.
- What standards you will set around the types of outputs and how you interact with the other teams such as development.
It also depends on whether you are a company doing in-house products, or whether you are a consultancy doing work for other companies. If you are in-house then having these can help because you will then get consistency across the products and the look and feel:
- A pattern library
- Component library
- Visual design: such as font, colours, icons
But the most important thing is that everyone has a unified view, that terminology and things are consistent between groups.
We are also working on getting code in our wiki too for the components and patterns :).