In Pokémon HeartGold and SoulSilver, you first have to defeat Whitney (the Goldenrod Gym Leader) in a Gym Battle. Next head to the Flower Shop in Goldenrod City and talk to the lady there. She'll give you a SquirtBottle. Take it to the Sudowoodo and use the SquirtBottle on it. It'll challenge you to a battle. Defeat it or catch it and it'll be gone.
you get a baby ditto
They won't leave until after you have beaten Blaine (and maybe Blue/Gary as well)
it is where if you leave to go to the next town it is blocking the road or out of the park to the east
Once you get an eevee from Bill. (House in Goldenrod City gives one for free) take it and a ditto to day care. Leave them in there. Soon there will be an egg there. Hatch it to an eevee.
you scare away the legendary pokemon and then leave
to find meteorites and crystals.
Never
You should leave out Togepi. They are not that strong and don't have very good moves. You could leave out either Onix or Sudowoodo. Or you could leave out Poliwrath or Quagsire.
Yes, leave 2 at the Day Care Center.
To get a pichu egg you must first caputure 2 pichachus that are genders in a different game such as Veridian Forest in Heartgold or Soulsilver. Then transfer them to your Black or White game. leave them in the Pokemon Day Care for a while. After a unknown period of time an egg will apear.
Even if you leave Johto Entei and raikou will still be there.
The next Pokémon HeartGold and SoulSilver event will be starting on Saturday July 31, 2010 and ending on August 27, 2010. This event will let you download the Enigma Stone over online Wi-Fi Connection for all English players. Once you get the Enigma Stone, you take it to the Pewter City Museum and you'll be given an item called the Soul Drew and once you leave the Museum, a Pokémon from the Hoenn region will be ready to attack you. In HeartGold, it'll be Latios and in SoulSilver, it'll be Latias.