The DS relies on friend codes for adding, well, friends. Here's my codes:
Metroid Prime Hunters: 4382-0448-7571
Phantom Hourglass: 3909-5654-0154
Picross DS: 171913-932582
Comment with your code and I'll add you.
The Wii also has a similar system, although here you use one code across all games: 1528-2710-1226-9571
Again, comment with your code and I'll add you. I've got a bunch of Metroid Prime 3 friend vouchers in want of a good home.