Newbie-but-learning husband-mechanic here. Here's a list of things that I've had to do to get a bike to shift well in all the gears, when it seems to be shifting and running quiet in most of the gears. Some is tongue in cheek, some might be helpful, your guess is as good as mine as to which is which because I'm lost half the time I'm fighting with my wife's bike.
Replace cable.
Derailleur high and low limit.
Turn the barrel adjuster one click one way or the other.
Re-tighten the cable, especially if you (or I) installed it. I use pliers to pull tight while I turn screw to clamp it to rear mech. Repeat, after you do it wrong the first 3 times.
Turn the barrel adjuster a few clicks to re-index.
Yup still makes noise in that one gear.
Take wheel off, get derailleur hanger tool out. (expensive! also worth it) Straighten derailleur hanger.
Remember B screw. Play with that a bit. Set it so derailleur is as close as possible to cogs, but not so close it makes ugly noise when shifting into largest (easiest) cog.
Still makes noise.
Adjust B screw out just a bit. Twist barrel adjuster exactly one click one way or the other!
Bam, perfect shifting. That was earlier this week ;)
Dr. Alex Harrison | Founder & CEO | Sport Physiology & Performance PhD
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