You walk around for around 50000 paces. A good place is the Route that goes through Solaceon. There's a straight path that is the longest straight path in the game, around 100 paces long.
you run around sinnoh and it will hatch.
run around
Yes
Run around as much as you can to make it hatch.
You have to walk around with it. It will hatch faster if you have a Pokemon with the ability Flame Body.
you can't hatch a pikachu egg on diamond, it hatches in to a pichu.
The number of steps needed to make a egg hatch in Pokemon Diamond depends on what the Pokemon is. On average it can take roughly 6000 steps to hatch an egg. You can cut the number of steps need in half by having a Pokemon with the ability Flame Body or Magma Armor in your team with the egg.
you walk around for ages and ages and it will eventually hatch
You must have a Pokemon with magma armor or flame body the it should make the egg hatch 1/2 the time
You have to have the egg with you and walk several thousand steps.
I don't think there is!
It depends on the Pokemon you are hatching.