Mine would eat from my fingers when I was in exams or during holidays, both times when I'm around him pretty much 24/7 and talk to him during breaks etc. it took a lot of time though. Numerous days in a row where I'd first have him come to the front of the tank before I'd feed him. Then I wouldn't feed him until he came to my hand on the outside of his tank. Then I'd hold a bloodworm half in the water and half out. Finally I could put a pellet on my finger about a half inch above the water and he'd eat from my finger. Each of these exercises took days, and a LOT of patience. Sometimes I'd sit holding a bloodworm for 15 or more minutes. It's well worth it though. However, when you stop doing these things, like I did when I got busy again, I found he'd stop doing them too. I try it occasionally recently and he won't - I may have to "retrain" him - but it will take less time the second time around.
A big part of it though is also how much time you spend with him. I would bring my laptop over and watch tv with him (Which believe it or not, betas will watch) on holidays too haha.
I also taught him to wave

When I come in and wiggle my finger, or he meets someone new, he wiggles his fins super fast, and it looks like he's waving. I also do it when I leave the room. When he waves when I wiggle my finger, opposed to "constant waving" or no response, he gets a treat, which reinforces the behaviour.
I'm currently trying to get him to blow kisses back at me

It OCCASIONALLY works. But I suppose mimicking a humans mouth movements is probably pretty hard, especially when he's used to talking and seeing a mouth move with that, so he has to differentiate between the two.
Anyways, I hope that helps you!

It's really just like training any other pet to do tricks, and familiarity is a really big factor too

Good luck!