How can I get candies?

You can get candies by:

1) Catching the Pokémon type. E.g. catching a Pidgey will get you 3 Pidgey candies. If you catch a Pidgeot you will also get Pidgey candy, and probably 4 or 5 candies since you caught an evolved version of that pokemon.

2) Hatching eggs. There is no definitive answer to how much you get as it seems to be random, but you can get around 8 to 15 candies of that Pokémon you hatched.

Update:
On hatching eggs:
2KM egg: 5 to 15 candies
5KM egg: 10 to 21 candies
10KM egg: 16 to 32 candies

3) Transfering pokemon gets you back 1 candy of that kind. Bear in mind that the Pokémon will be removed permanently.

4) Evolving. You get 1 per evolution.

5) Using rare candy! A rare candy can be given to any Pokémon. You can get these in various ways:

• Completing a week worth of daily research tasks (chances of getting them are random).

• Monday 9 am walking tasks. Walk 25km or more in one week. If you walk 5km, you just get Pokéballs. If you do 25km, you get the Pokéballs and various other items, with a chance of rare candy, and 50km is 25km prize + extras. Again, more rare candy is a 50/50 possibility.

• Winning a raid. I used to think the higher the tier of the raid the more rare candy you got, but this isn't true. Sometimes I've got 6 from a 5 tier, and sometimes I've got 1. They seem to be random. This can also be said about different tiers.

• Given as rewards in daily research tasks. There is one currently that says hatch 5 eggs with the reward as 3 rare candy, although bear in mind these tasks change up every 3-6 months or so, so if you're reading this in a years time it's possible it doesn't exist.

  All rare candies can be given to any Pokémon you have so if you're wanting to evolve a Pokémon you have that you can't find in the wild anymore, rare candy is much handier than catching them.

6) Use Pinap berries (yellow pineapple berries) when catching a Pokémon. This will give double the usual amount you catch. Also, note that during some special events, Pinap berries can give more candies than expected.

7) Add the pokemon as your buddy. Walking your buddy will get you 1 rare candy per amount required. Some pokemon only require 1km, while others are 3, 5 10, and even 20. Walk these are earn 1 candy per distance required.