I've developed my own ways of being very discreet with my disorder, I've only told a few people and got tired of hearing "you're too pretty to be autistic!" And "oh that's not true you can't be!" ..I'm not a social person and don't warm up to people, so nobody but a few people has ever had to witness a fit. That doesn't mean I don't have tiny fits anywhere I go, I just hide it incredibly well or its so small it's unnoticeable. so here's a list of what I can't stand, and how I cope with it, sometimes at home sometimes in public...

- too many people talking at once 
(How I cope) 
-ear buds! I wear earbuds in public and listen to music, it keeps me focused on what I'm suppose to be doing. 
-if I'm at a bar or out with friends and it gets to be too much either rub my rock I carry with my hand under the table, or I tap my fingers to my thumb in procession then backwards. (Pointer,middle,ring,pinky,pinky,ring,middle,pointer,etc)....most people don't notice it and those who do don't ask. I'll also "play piano"...I'll play a tune in my head and "play" the keys on my legs or the table/rail in front of me. I do this at cash registers too.

-utensils on plates/ teeth scraping utensils/ sound of people chewing
(How I cope)
-I hum a comforting tune
-bounce my leg
-chew my lip
-tap at my thigh 
-flap right hand under table while left hand is used to eat
-click my tongue against the roof of my mouth
-tap utensil against plate or table in a rhythmic way to focus on just that
-if it gets to be too much and I'm not in conversation, earbuds! Music is my main coping mechanism. It's one thing that has ALWAYS calmed me down.
-count the tiles on the ceiling or find patterns in the walls

-people breathing through their mouth
(How I cope)
-focus on my breathing and try to ignore theirs
-focus on not staring at their mouth
-finger procession tap
-if it's too much I will kindly ask them to please not breathe through their mouths
-if they're congested I understand and just remove myself from the situation

-buzzers/bells/alarms/abrupt noises
(How I cope)
-there is no coping in these situations for me, it's so startling and disturbing to me, I immediately cover my ears and shout "LOUD" repetitively, and voice how it's too much while I scramble to find a way away from the sound. I've gotten myself cornered and lost in situations like these because my brain is so confused and wanting to flee. I'll usually tap my palm against my ear to make a sound other than the current sound, but nevertheless I do flee in situations like this. I panic even when my doorbell rings because it startles me.

-people putting something/their hands in my face
(How I cope)
- I'm not one that likes people getting close to me or putting things in my face. When this happens my instinct is to bat it away, so I slap wildly at the object or person.

-random touching without consent
(How I cope)
- I lock up, but if I think about a song I feel better and don't throw a fit.
- I'll blurt out "please don't touch me don't touch me don't touch me..." and keep repeating it until I'm calm
-shrugging away when I notice someone is coming in to touch me usually is a good indicate of my lack of wanting any kind of human contact.

-the smell of food cooking
-I'm repulsed by food/meat..I don't know why but it disgusts me, I rarely eat cause I don't like the smell, when I do it eats usually not cooked vegetables, if I can stomach the smell of veggies cooking I will eat them though, but I never know when that could be. If I'm in a place where I have to smell food cooking I'll smell my shirt. I tend to drown myself in perfume before I leave my house so if I smell something unpleasant, I'll wad up a piece of garment and smell that instead. I'm aware it looks rude but it's less rude than throwing up in front of people.
-excuse myself outside for fresh air. 

-rapid light 
-I go to a lot of live shows and live in a place where there's flashing billboards, so I've gotten my fair share of having to see these things. They're distracting and I focus on th then start stimming, which I try to avoid in public. I'll usually just stare at it and dig my nails into my palm for sensation...if I can focus on a pain, I won't flip out over the horrible lights 

-I don't like opening doors or touching doorknobs. I really dislike the feeling of metal. And they're germ riddled. So I use the hem of my shirt or stand around til someone opens the door to enter and slink in behind them. For push doors I hip check them so they fling open and I can get by quickly

This is it for now. I'm sure I can come up with a lot more but I don't like talking a lot about things I don't like, I'm sure that makes sense haha thanks for reading and I hope this helps anyone else who has problems with stimming and going out in public