I took the slack out of my front derailleur cable in low. ... this was a bad idea. The cable was configured such that it had ... well, quite a bit of play. There wasn't actually any tension in the wire, at all. In fact, there was a LOT of extra slack: I took up an inch and a half easily.
I wound up putting most of that slack back to get it to shift correctly. There's also two screws on my derailleur that appear to be unmarked limit screws, but the docs tell me about these:
I guess I need to run through all this to get indexing and shifting right; but why so much slack? Is that just because my derailleur is horribly adjusted and I need to fix it? What am I missing here, besides any skill or experience or any clue about what I'm doing?