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There's no specific way for a certain type of DS, so I'll just tell you how to do it in general!
Okay so you go to the lady on the left at the back of the Pokemon Center. Make sure you have two DS', because you can't do it with just the DSi. Just join the Union Room and touch the trading icon, then do the same with the other DS and meet up with them, using wireless. If you'd prefer not to use wireless and you'd rather use wifi, go to the lady in the middle of the back of the Pokemon Center and speak to her, she'll give you a friend code. Then use your pal pad given to you back in Striaton and open it in key items. Do that with both games on each DS and add in their friend codes (the friend code is listed in that menu) and then go back to the lady in the middle, then you'll enter the room to trade and you can transfer between the games! n_n
Use the Quick Questions thread for any further questions, okay? :3