From what we've seen in the Nintendo Direct, this is how villager move ins will work, or at least how I believe they will work:
1. Interested parties: Nook will inform you of interested parties, and you will select one of them, which are likely randomly generated. Basically, you get x number of random move ins, but can choose which will move to your island.
2. Nook Miles Tickets: You can come across random villagers while partaking in exploring the smaller deserted Islands via Nook Miles tickets. You can invite them to your island.
3. Campground: Basically the same as New Leaf.
4. Amiibo Cards: You can invite a chosen villager to your campground, and invite them.