If in Act I you have a pistol hanging on the wall, then it must fire in the last act. --Anton Chekhov
The term Chekhov's Gun has its own Wikipedia entry, as I discovered as I was trying to track down the exact quote. (As it turns out, there is no exact quote, since Chekhov reiterated the point in a number of places--I used the quote from the footnotes to the entry.)
The point being, if you introduce an element into a story, then you need to follow up on it. I just changed two lines in the novel, simply because they hinted at something that ended up not happening. At the time I wrote it, things were still in an open-ended state of flux and it was a distinct possibility, but ultimately there was no need for it to happen and it didn't.
So I cut the line, replaced it with something that emphasized what did end up happening and I could feel the whole thing weaving together a little more tightly.
There are still a lot of loose spots that need to be tightened (or cut!) but I'm feeling more confident with each change that this thing could indeed be shaped into something worth reading.
I've also been going through the slightly embarrassing process of what might be termed de-Sue-ifying my narrator. There are, I must confess, a few too many times where she is reassured of her wonderfulness in the course of the draft. Old fanfic habits die hard, I suppose. So I'm paring those down and trying to make people's reactions more like those of actual human beings (where applicable.) Having seen the horrors that result when the author identifies a little too closely with the narrator, I know I have to watch myself.
I also have to be careful I don't end up spending more time blogging about the process than actually engaging in it.