This is such a good thread, and honestly, the same could be said for a few artists! Mosts "Artist looking for writer" posts get more offers and replies than writers do, but some of them are just so vague and don't even give examples of their art. I saw a post less than a month ago where OP (artist) seemed really rude and unpleasant to work with in general. If you're looking to work with other people, you should try to come off as friendly as possible, or at least someone easy to work with.
Another thing to add is not to constantly create new collaboration posts about the same project while expecting replies (both writers and artists). I'm sure more than half the people on tapas forums aren't looking for free job offers, so making more posts won't really go anywhere.