Start with the topic and intended audience, then pick a small set of tags that honestly describes the content. A hashtag generator can suggest options, but discard generic or misleading tags even if they seem popular.
Read the tag as someone who might click it. Would the post satisfy that expectation? Check platform rules and length limits, and avoid tags that are difficult to parse or ambiguous when words run together. Use capitalization to make multiword tags easier to read where supported.
Relevant tags improve discovery; a long pile of unrelated tags usually does not.
Akousa