how can I find the right hashtags eg on Twitter for my topic where my posts are best found? How can I determine how many times a specific hashtag was used in X period ?
I would examine "how i would find this content" as a starting point, then I would examine competitors and like minded people and see what tags they frequently use (after all they are probably paying marketing $$$ staff so they aren't frequently hashing the same tags for no reason) .
Lets say you have 10 hashtags to determine their value
Post 10 posts with 1 hashtag in each of them
Then take a look at each post and analyze its stats
That's it!