Instructions
Find the Pokémon Day Care and drop off the two Pokémon you wish to breed. A list of Pokémon Day Care locations is included in the Tips section. In male-only or genderless species, you will need to drop off a Pokémon with a Ditto, a Pokémon that possesses only the ability to transform into other Pokémon. Males only contribute "Egg Moves," moves that can only be learned by breeding. The female in a breeding equation will always determine the species of the resulting egg.
Check to make sure that the two Pokémon are compatible by speaking to one of the Day Care owners. Which owner determines compatibility varies from game to game, but they are often close to one another and easy to check.
Leave the Day Care and pace in the road out front. You must not be on a bike, as bike movement doesn't count towards steps taken and this is the measurement used to determine egg-breeding times.
Check back with the Day Care owners. Depending on which version you are playing, the one who is holding the egg may actually come to you or call you if you cross their line of sight. Otherwise, you will need to speak to them. Who carries the egg also varies, but can be easily determined by speaking to both owners.
Select "Yes" when asked if you want the egg in order to accept the egg into your party. You must have an empty party space for each egg you wish to carry, or the Day Care owner will refuse to give you the egg until you make room.
Begin walking to accumulate steps. Just as during the breeding process, the time an egg takes to hatch is measured by footsteps, so riding a bike will not count towards hatching the egg. If you are mass breeding, or breeding many eggs in succession, it is probably best to pace outside the Day Care. If you needed only one or two eggs and are ready to continue your adventure, simply move on to wherever you need to. Just be sure to walk instead of flying, surfing or riding your bike, if possible.