If you read nothing else here, read this.
The premise
Hashtags are a classification and search signal, not a reach lever. Optimise them for accuracy, not for volume.
The structure
Three to six tags describing this specific post. Three to five describing your niche, stable over months. At most one or two broad tags. Rotate the first group every post.
The counts
Instagram eight to fifteen. TikTok three to six. YouTube three that matter. Facebook two or three. X one or two. LinkedIn three to five. Pinterest around eight. Threads exactly one.
The ladder
Weight toward tags you can realistically rank on. Mostly low and medium difficulty, a couple of competitive ones, rarely anything saturated. Shift the ladder upward as your account grows.
The checks
Search any unfamiliar tag on the platform before using it. Look for recent posts, relevant content and no restriction warning. Thirty seconds each.
The system
Keep a library organised by the kinds of post you make. Rotate within groups. Review quarterly. Write down what you learn.
The thing that matters more
The first line of your caption, what you say out loud in the first three seconds, and whether the post is worth sending to a friend. Tags are the last ten percent of a post's discoverability. Spend your time accordingly.