There's this little icon atop the text, right between the heart for 'Memory' and the letter for 'Tell a Friend', showing a little pencil with a tag? That is 'Edit Tags'.
If you click on that, you get a list of tags that the community already has. Try sticking to that instead of entering your own, so each charrie has exactly one tag. It got away from people over in Milliways, and as a result, the tagging system was all in a shambles when LJ suddenly decided to limit the different tags per journal and comm to 1,000.
Also, if you find Charlie both under 'Chas' and under 'Charlie Shaw', tagging becomes a bit muddled, as you wouldn't find all his threads under the same tag, which is precisely the point in tagging. We don't have a thousand tags, though -- as we don't have as many charries. In Milliways, there are seven different Charlies that have tags; here, it's just the one, and everybody knows him, so his tag is 'Chas'.