I have tried tuning a "clicky" rear derailleur a few times now and always seem to forget the stuff I had learned the last time. So I decided to write down the lessons learned so that hopefully I will not repeat the same mistakes next time.

1. Make sure the barrel adjuster on the shifter is in the middle of it's range, neither fully tight or loosened. This means you can use it to make small adjustments if needed later.
2. Place the shifter to the highest (smallest gear) ring and tighten the cable at this setting. May need to loosen later so no need to tighten it too much.
3. Move to shifter to the top, being careful not to send it over into the hub.
4. Check the max limit by pushing the hanger out into the hub and make sure that it does not move. If the hanger arm is able to move further out, then it can fall into the hub when cycling so loosen the outer screw to bring it in. If the hanger arm is sitting inside the natural line of the biggest cog, then tighten the outer screw to push it out.
5. After than tuning, the cable may be a bit slack now on the biggest ring, so use the pliers to pull it tight and then re-tighten the holding screw to keep it in place.
6. Now run the shifter back down to the bottom and make sure it is aligned. If not, then use adjust the inner screw onto the rear derailleur to aligned.

If the chain is jumping, then try and figure out where it is jumping.

• If jumping at the front, then check if the sprocket is worn.
• If it is jumping on the cassette, then check for wear on the cassette. How do you know if it is worn? With great difficulty. Below is a picture of my old and new cassette side by side. The old cassette continually skipped when I had to put on a new chain, but the new one was fine. It's hard to tell the old one was worn.
• If it is jumping feeding on the cassette, check the hanger arm is the correct distance away when on the biggest sprocket and tune accordingly.
• If it is jumping on the jockey cogs, then check if they are worn and feeding into the correct narrow/wide parts of the chain.
• Changing a chain only when both the cassette and chain are worn is going to lead to skipping. So if both are worn, then change both.
• Make sure you have the right chain for your cassette and group set. If not, it can very easily skip under torque.
• If clicking like it wants to change gear, then it means the hanger arm is not aligned precisely with the chosen gear on the cassette. To fix this, either use the barrel adjuster up on the shifter (if you are out on the trail) or use the processes above to make sure the arm is aligned at the biggest/smallest gears (if back at the shed/garage/kitchen floor).