Hi @SimonTaylor_1ed1 - so glad you asked 
At the moment, we have configured Discourse to trigger the following events on every new topic :
- a tweet (under @thesagrid) is sent (using a few IF recipes)
- a message containing the topic title and summary is sent to a few channels on slack (using the Twitter app for Slack)
These are impersonal (ie, do not depend on the preferences of the user and are not sent directly to users).
Personal options
Category-level options
Discourse has a very flexible notification engine (see http://www.discourse.org/about/ for more info), but also tries to be polite, relying on the user to express their intention of following topics or categories. You can select explicitly set to be notified of events on a category by selecting your preference of that category. In this category e.g. you can set your preferences by clicking on the notification option area :
(the grey circle in on the right).
Clicking on that you get some options :
You can do this for every category you are interested in.
Personal preferences
You can also set preferences at a more fine-grained level, as well as enable other options, in your user preferences page
There are a few options related to notification below :
See also
So, I'm sure many other people had similar questions which perhaps just haven't been asked yet. The best place to get support for this kind of stuff is on the discourse forum
Some other topics there in a similar vein :
and the general search query
