For all of my fics, I label in the header for the following potential triggers:
rape, other consent issues (noncon/dubcon)
abuse (specific: child, spousal, or another; type: emotional, verbal, physical)
incest and incestuous themes
suicide and self-harm (specific: cutting, eating disorders)
addiction (drug use, alcoholism, smoking)
violence (specific: murder, to a child)
torture and captivity/war situations
infidelity (type: emotional, physical)
general dark themes
I will also let you know if any of these are graphic, non-graphic, or somewhere in the middle.
If you have a less common trigger and would like to know if it shows up in my fic, or if there's anything you think I should add to this list, please let me know in a comment or PM me.