Walking
yes tou can
yes
i don't have Pokemon emerald, but the answer is always the same. not how long. how many steps. walk ALOT and the egg will slowly start to hatch
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you have to just wait until the egg hatches - keep it in your party.
Breed a Wigglytuff hatch the egg to receive igglybuff.
No hatch it first then release the Pokemon inside if you don't want it.
Put a starter with a ditto in the Pokemon daycare and wait for an egg hatch it to get the baby starter.
run/ride around quickly. Once you've taken a particular amount of steps, the egg will hatch
You don't. Breed a marill holding Sea Incense and the egg will hatch into Azurill
Breed 2 marrils while one is holding a sea incense then hatch the egg.
It all depends on which kind of Egg; Riolu eggs take longer to hatch than say, a Caterpie Egg. To be sure, go to Bulbapedia.org or Serebii.net (must-know websites for Pokèmon Fans)