Pokémon Diamond and Pearl couldn't have gotten better when it came to connecting world-wide with the use of Wi-Fi. Located in Jubilife City is the grand Global Trade Station. The Global Trade Station allows for players to connect and participate in trades with anonymous users from around the world. In order to be able to use this service, you must have already obtained 3 gym badges.

Once you are connected, a cute menu appears on the top-part of your Nintendo DS screen.
You may search for Pokémon using there little search feature, which can come in handy when searching for the right Pokémon with the right gender and level. I only wish they could have added a search field to search by specific nature.

Just don't be too picky when searching.
If you are making a request, then it will show a simple form which allows you to specify what Pokémon you are actually searching for. In the drop-down, you may select a Pokémon that you would like, it's level and geneder. Including the Pokémon you are offering for it. Unfortunatly, you may only request Pokémon that you have already encountered.
An advantage to using this service is that you do not have to keep your Nintendo DS on in order for the trade to process, as it is stored in the server to which it is sent. If you ever have a change of heart, then you may call off the trade if it has not yet processed.

Er, same not-too-picky criteria applies for requesting trades as well.
Optionally