If you really just think about what you're sharing, it's likely going to fall into one of three categories.
1. I want to share this with my friends and family, it's ephemeral, will interest them, and expresses more about who I am.
2. I want to share this with my coworkers and colleagues, it is relevant to our professional interests. This category also happens to be the "Public" category for me in a lot of cases, because anything I share professionally, doesn't need to remain private.
3. Anything off topic here. Something that lands in this category (while interesting and relevant to you) is, for the most part, uninteresting to the audiences you've made yourself available to.