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.
About 10,000 steps. If you don't believe, then check your Pokemon handbook (instructions booklet).
You will need to walk/run/bike a certain number of steps to hatch the egg.
There is certain number of steps you need to make to hatch an egg. But you need to have an egg in your team.
it Depends what Pokemon you breeded together to make the egg
It is impossible to hatch an Ivysaur from an egg; therefore, no amount on steps will make eggs hatch an Ivysaur. If you bred with a Venusaur or an Ivysaur correctly, then the egg would instead hatch Bulbasaur.
To hatch an egg you just have to walk while you have it in your party, it takes a certain number of steps to make it hatch.
About 6400 steps. Try cycling back and forth on your bike to make it faster, or have a pokemon with the Flame Body and/or Magma Armor in your party with the egg(s) to make it hatch a little faster.
Put a Pokemon with flame body/magma armor in party and 500 steps
No, unfortunately only the abilities Magma Armor and Flame Body halves the number of steps required to hatch an egg in Pokemon Emerald and afterward.
It take approx. 5,120 steps for a Feebas egg to have. You could halve that if a Pokemon in your party has Flame Body or Magma Armor. That will make the egg hatch faster.
You get a certain Pokemon that cuts the steps you walk but it depends on the old versin of black or the new versin
You'll need to walk, run, or ride your bicycle with the Egg in your party. Each Pokemon has a Hatch Cycle, (Even No Egg grouped Pokemon) which shows how many steps required for the Pokemon to hatch. It doesn't display in-game, but helpful Pokemon sites can help you determine how many steps you need. You can also decrease that step amount by having a Pokemon with the ability Flame Body in your party.