Oh, I flat out tell people. I have a Pokemon card as a bookmark. Sometimes people comment about it.
I've recently 'gotten back into it' as an adult. As a middle school student, I was a big fan, and it got me a lot of ridicule from bullies. People would try to get a rise out of me by poking fun at my hobby. Eventually, I came to dislike Pokemon, partially because of the way that my peers treated me. It was a good scapegoat at the time. I packed all of my Pokemon things away in my parents' attic.
Then Diamond and Pearl came out.
The time came to purchase a DS early last summer. My first game, for nostalgia's sake, was Pokemon Diamond. My friends were quick to follow suit, and all the sudden, we were playing through the game we'd all enjoyed as children together. In no time, we were playing the card tournaments again at my friend's anime and hobby shop, discussing deck strategies and whatnot. With kids.
I once whispered to a friend while there, "I was a Pokemon fan before these kids were even BORN." It's funny how old you feel when you realize that your age bracket puts you in the "master" division during weekly tournaments.
Nowadays, my boyfriend and I will share an ideal evening after classes watching M*A*S*H and playing Pokemon. It's all shameless. We're 'big kids' now! It's great to find that common thread with your buddies again.