I have a lot of very visible stims. As a child in therapy they tried getting me to do one of the main ones behind my back, or under a table, or something like that - but it was impossible to do. The one I'm thinking of is probably my main one - I put both of my hands up to my face, elbows extended out and up - the backs of my hands are touching my cheeks - my pinky knuckles are at the corners of my mouth - fingers wiggling furiously. It's involuntary - I do not realize that I'm doing it until it's over. They tried having me do the finger wiggling under the table or behind my back but it just doesn't work at all.
I did, however, learn tricks to help prevent it from happening - which is to constantly keep my hands doing things. I basically just play with my hands to do that - just constantly moving them touching each other usually.
However this also attracts negative attention - I distinctly remember one time when a bandmate made a comment about me always fiddling with my hands - it seemed like a negative comment (I honestly don't care because they respect me very much as a musician and that's all I care about). It may have been said playfully or something - but I don't know. My rocking has also been noticed. Fortunately while we are playing music I can just move along with it and they think I'm just moving to it but often I am literally rocking side to side to it - balance shifting from one foot to the other. I rock a -lot- when sitting - almost always back and forth rocking.
There are many other instances of truly negative attention but they are mostly limited to my elementary school, middle school, and high school years.
I've tried really really hard to lessen my stimming but it's had little effect. I must do it - and I've come to accept it.
If people ask me about it I just tell them that it's really complicated (so that I don't have to explain and say I have autism), and that it's involuntary.
As a kid I told them "I do it when I'm thinking really hard", which is often the truth - often if I am deep in thought I end up doing that main stim I described earlier. But that backfired horribly. I would do it, and then anyone I told that thing, would ask me "what are you thinking about?"... and I would just say "nothing" if I was able to talk at all at that point. I'd get angry at them, too.
Now I know that I shouldn't have gotten angry at them - it's a -VERY- strange thing that I do as far as NTs are concerned - and it's only natural for them to be curious about it.
In retrospect I am sad that I got mad at those people - they were the ones that DIDN'T make fun of me about it - they were trying to be friendly about it and ask me things about it, find out more about it. When I think back, in every single case, those people were people who were pretty much always friendly to me. I've had people explain to me in detail about what a NT's thought process probably is when they see me do that.
But now I just avoid the issue and say it's complicated and involuntary, and thankfully most people leave it at that.