This is hard to describe, and it's something that I unfortunately do as well -

Sometimes there seems to be a sense that the responses are keeping the thread going just for the sake of keeping it going. That there isn't any direction to it, and that it could have been wrapped up neatly several tags ago.

So, don't be afraid to wrap things up or nudge them toward a logical end. As I mentioned, I sometimes keep things going past the point that it's really necessary; sometimes it's because I want to keep playing with that person even though the thread is pretty much played out, other times it's because I just can't think of a good way to end it. So, I need to get better at endings.

One thing that I like is when the other player has some idea of a direction that they want to take things in. It's easier to get a good thread going if there is an actual point to the conversation.

Oh, one more thing, mostly applied to beginnings - I like tags that have some kind of dialogue or action in addition to internal narrative. It's easier for me to respond to things (both as Anon and as Norway) if I have something to respond to, because my character can't read your character's mind.