[dentalperson]

I love the math/stats history around gambling-related things, thanks for mentioning this. This method assumes the flipper can't introduce bias. ET Jaynes in his book Probability Theory also mentions that it is easy to learn to flip a fair coin in such a way that the result can be predetermined. I searched a tiny bit for this but couldn't find what he was referring to though.

[aspenmayer]

I’ve heard that, with many hours of practice, dedicated amateurs and many famous magicians are able to do this kind of thing. I wouldn’t call it sleight of hand, but it is similar, although it may fall under that category broadly. I’m not a domain expert but I was taught some simple coin tricks as a child by my artist mom’s artist friend who ran the local frame shop. I never tried or thought to try to favor the coin flip or introduce bias, but it’s definitely a skill that can be acquired.

[kqr]

I remember at one point in my childhood learning a trick where it looks like you're flipping the coin, but you're really only causing it to rotate and wobble, meaning it's guaranteed to land on whatever side faced up as you tossed it. I don't remember how I did it though, and a few minutes of trying to recreate the effect has failed.

[ryanar]

Lots of practice, use your thumb to hit the edge of the coin to give you more control, aim for a specific spot so you use the same amount of force and control the amount of times it flips. You can also use a surface that absorbs more so the coin is less likely to flip after hitting it.