How to fix a loose flush handle on a toilet

Questions covered in this video:

1. How do I fix a loose flush handle on my toilet?
2. What causes a toilet flush handle to become loose?
3. What tools are needed to tighten a loose flush handle?
4. How do I access the nut that secures the flush handle?
5. Is the nut on the flush handle reverse threaded?
6. How tight should the nut be to secure the flush handle?
7. How do I test if the flush handle is properly tightened?
8. What are the risks of not addressing a loose flush handle?