Humor a nit. How and when did you learn you could read other players hands?

I have come to grips with the fact that poker is not my strong suit. I REALLY love the game, but I plateaued at sub-mediocre play years ago and even with lots of table time in live cash games, I'm not getting better. I play low stakes for fun at this point, but I have given up my dreams of ever "hanging with the big boys." (I don't mean going pro, just enjoying a $200 buy in or something like that).

I can not understand how to read hands. When someone calls out anyone else's hand, I'm sitting there like a goddamn idiot with my mouth hanging open like "B... b... b... but... the cards were upside down!" The entire table will call out in unison "King ten off" and I'll be sitting there going, "WHY DO YOU KNOW THAT!?"

I can play MY cards, sure. I know when it's worth it to call on a draw. I know safe places to raise. I know how to play when I do hit. I can avoid conflicts, etc etc. Who gives a shit? That's not winning poker. That's not even surviving poker.

so let me respectfully ask those of you who can read what the other players have - when did you realize you had this awesome power and how much work went into it? Did it come naturally? Was it a lot of off-table research? Did it come from just "feeling" betting patterns? Did it come over years? Months? Days? Do you give "tells" a lot of credence? Are there types of players you can't read? What do you do then?

I'm not looking for lessons. I could go read Mike Caro or Super System cover to cover and none of it would sink in. I'm just curious about your personal experiences and I hope people will reply in the good spirit that this post was intended.

Check.

Sorry, force of habit.

EDIT: Thanks again for all the replies. I have read and thought about all of them even if I can't reply in a knowledgeable manner.