How do I properly perform a rear derailleur replacement on my bicycle?

To properly perform a rear derailleur replacement on your bicycle, follow these steps:

1. Shift the chain onto the smallest rear cog.
2. Use a chain tool to disconnect the chain from the derailleur.
3. Remove the old derailleur by loosening the mounting bolt.
4. Install the new derailleur by aligning it with the derailleur hanger and tightening the mounting bolt.
5. Reconnect the chain to the new derailleur.
6. Adjust the derailleur's position and tension as needed.
7. Test the gears to ensure smooth shifting.

Remember to refer to your bicycle's manual or seek professional help if needed.