2. Practice mindful meditation and practice other techneques for calmness
3. Slow down a lot...walk slower...talk slower...mindful meditation helps with that.
4. Keep careful track of your cycles so that you know your pms time...even if you don't suffer seriously you may be prone to being less patient then(this is the only time I yell..yes, it became that obvious to me)
5. If your trigger is messes...don't have crafts/waterpaints/messy things in the house...take them to other places for that. We do those things outside and we have a regular playgroup for that stuff, we have crayons and markers but if we do that sort of things it's planned and organized. Work with who you are and what your limitations are. (I have a no play dough rule because it always gets stuck in the carpet and I lose it and I figure it's just toxic junk anyway..and I hate the stuff)
6. If your trigger is noise(mine isn't noise so much as sudden noise that startles me) teach your kids inside and outside noise. Also designate an escape area for you to go to when you feel that urge. I go up to the living room and sit. I'm fortunate in that we have the basement as a family area and a quieter upstairs living room.
7. Take regular and scheduled breaks for yourself. Half an hour walk every night. I joined a rowing club and I go once a week, no kids, just me. It's amazing and the thought of that break often gets me through when I'm about to lose it.
8. Sing. I start yelling and then change it to a fake yell and then into a silly song and it cracks the kids up and changes the entire dynamic of the room. It's crazy but somehow it works. Probably like the whispering that someone mentioned above.
Eta...I rarely yell. Because I rarely yell my kids yell less. It has taken work but it was well worth it. I really have a ton more patience. I used to talk about real and fake patience...the fake it til you make it works..because I find that I rarely have to fake patience, I just now am more patient and rarely lose it and yell anymore. In fact I was really angry at my 15 year old for something she did and I was talking about how much I yelled and screamed at her but looking back on her..it really wasnt' yelling or screaming. It was lecturing sternly but it wasn't yelling. And what she did was off the charts crazy dangerous(which is also a trigger for me).