What I've done, in Canada, is waltz into my local EB Games. Then, one of three scenarios occur:
1: The Poster
A big ol' poster with a Pokémon on it announcing the event. It will either have the required serial code, or simply say that it can be received wirelessly at the location. This is how I've gotten the Shiny Sinnoh trio and Genesect and is how most in-store events occur.
2: The Conversationist
I go up to the dude or lady at the counter and go "Yo, homie G, what's cookin'. " and then they go "Not much man, you here for the Pokémon?" and then I go "Yeah buddy," and they go "Hey man, here's ya Pokémon." and I go "Thanks bro," and they go "Respect." and I say "Peace out homies," and moonwalk out of the store.
(Okay maybe not quite like that. But you get the point: I ask the workers for the goods.)
3: The Disappointment
No poster. No homies. Just blank looks and the unshaven, overtired employee going "Uh, I don't think we have that. Sorry." Then I walk away disappointed.
SOURCE: My life.