For each group of miis presented to you, click one or more of your favorites from that group and press the "Pick" button. Eventually, your favorite miis will start appearing under "Found Favorites". You can continue as long as you like to construct an arbitrarily long list of your favorite miis.
In principle, the result will be perfectly accurate, provided you pick consistently - you'll correctly get your second favorite second, even if it's pitted against your absolute favorite early on. You can also reorder your favorites after they've been added onto the list.
Include miis from: