Until we get to that stage of the code rewrite, and tags are given a separate field, it's going to be difficult. Authors need to juggle between a summary to attract readers and tags, and as a writer myself, the summary is difficult enough in so short a space. Many of our authors actually tag at the top of the first chapter, because they simply can't fit a summary an all necessary tags into that field.
Now, having said all that, if you give me an idea of what you're looking for, I might be able to assist in narrowing it down. I used Bi, Bisexuality simply because it was the first tag on the list that was under four characters.