How do you effectively practice yomi?

To practice Yomi, you have to give David Sirlin $100 for the 1st editon.
J/K. Don’t buy that game. Well… unless you really want to pay $100 for a card game. Nothing against the game personally, but I would have an easier time buying a $50 poker set and actually getting people to play me.

Back to Street Fighter:
You really need to just play the game, and learn the match-ups.
Just to be clear “Yomi” is the literal translation for “Reading” in Japanese.

So to give an example of Yomi at work. In SSFIV:AE
Let us say you are an Adon main playing Hakan who has an Ultra II. Now say that you damage him with a lot of jump in cross up combos and he builds a Ultra II.
Now his reading of the situation is that you like to jump in a lot and he is buffering that Ultra II motion that beats jump ins all the time.
Because you see the Ultra II you now know it is not safe to jump, nor do any of your specials that leave you airborne.
No Jaguar anything because Ultra II will beat all of those.

The low risk thing to do is to now play a ground game and can only jump when you think they are not going to react to it. Now if they can capitalize on the fact that they know it is not safe for you to jump, they can go for a lot of options that the best solution is to not jump, say go for grapples.

So now there are a few things you might try to test them if you want to take the risk.
Now if they are a newb, maybe they don’t know Adon at all and don’t understand that Jaguar kicks can be ultra 2ed. Maybe you can score a hard knockdown and early safe cross up jump to land early and bait the Ultra 2.

Of course, if this is your opponent’s first time playing and don’t know how to play Hakan or any of his special moves, and needs to look at the command list at the beginning of the fight, then all this reading goes out the window because they are ignorant of the matchup, and maybe vice versa.

So it isn’t about only knowing your characters, and the matchup, it is also knowing the other player and what they are capable of.