Make a Nintendo Network ID
Out with the friend codes, in with the Nintendo Network. Nintendo's terrible friend codes, randomly assigned 16-digit ID numbers that made it a pain in the ass to add friends on the DS and Wii, have been replaced by the Nintendo Network ID.
Yes, Nintendo has finally caught up with everyone else in this regard: you choose your own ID, just like on Xbox 360 and PS3. And adding friends is as easy as typing it in. Welcome to the modern age!