Thanks to The Mystical One for sending me the updated values for the triggers, and thanks to yab for gathering all the info.

When taking an action:
Base chance: 1%
Vocation is Martial artist, Ranger, Luminary: +1%

Equipment bonuses (after action only):
Critical fan: +6%
Overcritical fan: +7%
Hypercritical fan: +8%
Dire critical fan: +10%
Combat action medal: +3%

When getting hit:
Base chance: 0%

Damage taken (out of max HP):
10%: 1%
20%: 2%
30%: 4%
40%: 8%
50%: 16%
60%: 32%
70%: 64%
80%+: 90%

Other party members' CDG (action & getting hit):
1 member ready: x2
2 members ready: x3
3 members ready: x4

(bonuses are added before the multiplier)