If I am missing any good point in the list please post it. Let all good techniques be added to this list.
My list is in the FAQ


Techniques to improve EMC of system.

I would title this group
Techniques to reduce EMC sensitivity of system

1) not all of us use 470uF

2) "radiation" in this group?

3) there are other isolation techniques than opto

5) not to the enclosure, but to the main ground point as you say in 6). 5) contradict 6)

7) I would never do this, it effectively let the encloseure radiate through

9) shielding behind e.g. the LCD is much better. If you put the LCD outside the enclosure you add ~10 wires to pick up EMI


Good PCB layout Techniques
most of these do only apply to boards without solid ground plane (4 layer) that should be stated


7) is EMI reduction

Techniques to redcue EMI of system
I would title this group
Techniques to reduce EMC radiation from system.

Erik