Have an idea? Write it down. Made a plan how to tackle something? Write it down. Disagree with something? Write it down.
Writing is brilliant in that it does two things at the same time: It makes you express something in a form that is easy to consume for others, and it comes with a built-in commitment that what you mean at a given point in time moves out of your brain, into a rather fixed state. Writing is the single best thing you can do to enable true collaboration.
One of the highlights of working at Shopify was the writing culture. There was a text document for almost anything - and people would work in those documents. Comment, Redo, Share, Quote, Decide, Approve. At one point, it became second nature to simply start writing in a google doc and share as the document developed into a more presentable form. You moved from idea to thoughts, and then to a first draft. All within the same space.
It makes a ton of sense to work like that if you think about it. There's speaking or discussing work, referencing work and then there's the actual work. Writing things down is actual work, it costs time, it's tedious and it forces you to decide on many things - words are rather specific. Having a writing culture creates a shorter path between initial ideas and the progress on the way to a solution.
More importantly, there's the aspect of enabling asynchronous collaboration. You can read a document whenever you want to. The author can be offline, on vacation or simply refusing to speak to you - in a transparent organisation, artefacts are accessible and available to most people. That enables not only the consumption of one single document - super valuable. It also allows for the discovery of arbitrary documents that might help to gather more context for past and present decisions.
The alternative to having a transparent record of past activities is the move of actually having a call with someone that shares context for an hour. That also works, but it costs a lot of time, and whenever that person is not available - good luck.
Lastly, I personally feel that clear writing can only be achieved if your thinking is clear. I admit, my thoughts here aren't always as clear as I'd like them to be, but the general impression I'm having is that having to write something down helps me in structuring, sorting and clarifying my own thoughts. That usually leads to not only better writing, but also ultimately, better decision making.
Speaking of tools, I'd argue that whatever tool you're using, it should allow for some basic collaboration. Leaving comments inline, basic revisions and an overall ability to annotate content are crucial in creating documents that aren't just static repositories of information, but spaces for active collaboration, exchange and discussions. And ultimately, decision making. Google Docs, Confluence, Notion - all of those tools fit the bill. But whatever you decide on, just make sure you're actively using it. Saves a ton of meetings if you just write stuff down.