How do you get 10 villagers??

[ZoeNeko]

I've always only ever been able to have 9 at a time, and I think the maximum amount you can have is 10? How do I achieve that o:

 

[mintellect]

You can get ten villagers by either

Getting a move in from someone you streetpassed/had a wifi session with,
From the campsite or
Adopting a villager from someone.