We first learned about the Pokemon Go buddy system earlier this month and basically everything we heard has held up to be true. The main thing to understand here is that you get to select one of the many Pokemon that you've already caught and he (she? it?) can then accompany you on your walks to collect the corresponding candy.
If you've been having a hard time finding Caterpie to "transfer" for Caterpie candy to evolve your Metapod, for example, this could be a great way to do it.
You can only have one buddy Pokemon at a time, so the first thing you'll need to do is choose who will follow you around.
- Tap on your player icon on the lower left corner of the main gameplay screen.
- Hit the menu button on the bottom right corner.
- Choose "buddy" from the resulting list.
- Select your Pokemon Go buddy.
- Start walking.
The Pokemon Go buddy system uses the same distance tracking technology used for incubating eggs, so you'll probably end up walking further than what it says you need to do. Not all Pokemon and Pokemon candy are made alike, however. For some more common pocket monsters, you only need to walk one kilometer. For others, you need to walk up to five kilometers. After completing one cycle, you earn one candy for your buddy.
For example, since Clefairy earns one candy per kilometer and it takes 50 Clefairy candies to evolve into a Clefable, you'll need to walk a total of 50 kilometers to earn enough candy to complete the transformation, assuming that you don't catch and transfer a few Clefairy during those 50 kilometers.
But what buddies are the most "worth" it? A handy list has been compiled for all 151 Pokemon in the game (yes, including Mew and Mewtwo). It'll show you how many kilometers it takes to earn one candy, how much CP you're effectively earning on a per-kilometer basis, how many candies it takes to evolve, and how many kilometers it takes to evolve. The list can be sorted by each of these columns for ease of use.
That's the good news. The thing is that your buddy Pokemon doesn't actually "walk" (or fly or crawl or whatever) with you on the actual gameplay screen. It just appears as a little round icon next to your player icon, as well as on your player screen. The only rumored exception to this, at least for now, is Pikachu, but you'll need to walk 10 kilometers first.
Now, we just have to wait for Niantic to implement a peer-to-peer trading system.