You can exchange friend codes with someone and battle or trade from far away or go to the wifi battles at the battle tower in the Fight Area.
_______________________________________________________________________
Heres another question.
HOW DO YOU CONNECT TO WIFI?
and don't say "go talk to the lady in the basement of a Pokemon center"!
For realzzzz
_______________________________________________________________________
Open your DS and load to the Pokemon Diamond Startup. Press start and go to Wi-Fi Settings. From there on, search hotspot and choose the network you are familiar with. The setup is pretty basic and easy, just follow the instructions.
Yup.
yes
in jubilve city
because you need better wifi
you just can't
In Jublife City
Via Nintendo Wifi.
No, you need their friend code. UNLESS, you are in the Battle Tower doing a Wifi tournament. That's the only way without friend codes.
either by cheating or a wifi event (but wifi event expired)
its the card that enables you to use the wifi station in jublife city.
Of course you can. I played my Pokemon Diamond with my cousin that has Pearl.
You can trade, battle, and have voice chats with your friends over Wifi in Pokemon Diamond/Pearl, but to do so you need to know your friends' Friend Codes, and your friends need to know your Friend Code.