etiquette 201

we all know the main rules of etiquette 101:
1. guys opening doors for gals.
2. don't talk with your mouth full.
3. don't chew and make smacking sounds with your mouth open.
4. saying please and thank you.

what do YOU do when:
1. you notice someone's pants zipper is open, especially if it's a person of the opposite sex
2. the person you are directly talking to are eating while their mouth is full and eating with their mouth open.
3. someone doesn't wash their hands after they go to the restroom.
4. there's a piece of food on a person's face.

do you tell the person or keep it to yourself? if it's a repeat offense, do you just get really disgusted and not say anything?

i remember someone telling me when i was younger, that i smacked my mouth while eating. the harsh words still ring through my head. to this day, every time I eat I try not to chew with my mouth open, talk with my mouth full, or make smacking sounds. i feel like these three "bad manners" are related to the asian culture. i have seen a lot of asians with these manners. since i am so aware of it, i get super disgusted. i just try to deal with it. i feel like the disgusting sight is more worth it than telling the person and sounding rude. plus, if the person has been doing this all their life, they probably won't even change it even if it is "bad manners".

what would YOU do?