Unless you're famous, your best bet at getting a lot of people to rate your post is attracting citations, so that your post becomes a default reference point for that topic across the entire ecosystem.
Write in complete sentences. A complete sentence provides context and expresses a point of view, rather than just saying alien video https://youtube.com/9jf209mm2me....
Limit each post to 1 main idea. If a post has multiple ideas in it, it will be less useful as a citation because people might only want to cite half of your post, and won't be able to.
If your post contains a link, provide context. Summarize the link so people know what it's about without having to click it.
Think of posts as "nodes" rather than "replies." Even if you're replying to someone else's post, your post will also appear by itself without any context. If your post doesn't make sense by itself without context, it probably won't attract many ratings.