Hmm...well, I'd be grateful, since the real world is pretty freakin' boring.
I'd start off by finding out where I could get some new clothes and how I could get acclimated to the society there. They never mention any true form of government, so I'd guess it would be pretty easy to get taken in by someone until I could get some pokeballs and stuff I'd need for my "journey". I'd make up a fake identity of a mysterious vagabond or something to interest other people. I'd probably need to get a pokedex for registration purposes, so I'd try and find a used one and just hack it to my specifications. Then the real fun would begin.
I'd go the typical route of training up some Pokemon for battling, and grind them for months until they were really experienced and evolved. I'd then use this team to begin my ultimate plan; to take over the Pokemon world. I mean come on, if a preteen can single-handedly take down these crazy villainous teams in every region, then why couldn't I? I'd probably have to do some evil things, but I'd do what it took. Heck, I'd catch all the legendaries to make the task easier. Once I'd crushed Johto and became it's de-facto Emperor, I'd use my forces to subdue the other regions, until I had secured Sinnoh. Then I'd capture the Dragon Trio and use their combined powers over space-time to return me to this universe. Man, it would be so very easy to rule this planet, being the only person with Pokemon, muahaha!!!