It's simple. You click on a Pokémon and then hit the "Pick" button. Your favorite Pokémon will start appear under "Found Favorites". If you are safisticated with your results, post here in this thread!
I broke before I got a first favorite. I couldn't choose when it got down to Venusaur, Hitmonchan, and Mimikyu. Other close contenders include Hawlucha, Joltik, Articuno, and Durant (that little gal has saved my butt in a few challenges, and is now one of my faves).
1 It's a beautiful and elegant looking dragon, but it also looks kind, humble and sweet, unlike Serperior and Milotic which look more pompous. There's a deeper reason but it's explained on my AMA!
2 I don't really know what it Is about it, but I like the coloring and how it looks tough, elegant and graceful all at the same time.
3 I like the colors and the design. Never used it in battle but I like it. There's a sort of peaceful look to it.
4 It was my first real starter and I love its look. Basically it's a mix of attachment from the game and how it looks like a bear that's fierce but can also be tender if needed.
5 I expect by now the theme is clear. Graceful and elegant. A little less than the ones above it, but still so.
6 I like the concept of a Pokémon that can create illusions, and I've roleplayed a Zoroark character on at least two separate occasions. I like the colors (and it has a ponytail xD) and how it's sort of elegant in a dark, mysterious, menacing sort of way.
The rest are a mix of strength plus design plus using them in games or roleplays.