Here's some Frequently Asked Questions and the Frequently Given Answers:
Q1: Where is the Amulet Coin?
A1: The Amulet Coin is found in Amity Park, but is in a secret place. Go to the right entrance of the Amity Park, then walk to the far left, walk north, and open the item there and...bam! You got the Amulet Coin,
Q2: Where is the Griserous Orb?
A2: Go back to the Sendoff Spring and go through the chamber where Giratina used to be. In the room where Giratina used to be, in its place will be...the Griserous Orb.
Q3: How do you get Dialga and Palkia?
Probably one of the most FAQ's is where to get Dialga and Palkia. Well, here is the answer: Once all is done, including the Elite Four are defeated and the player has found both the Adamant and Lustrous Orbs in Mt. Coronet, Cynthia's grandmother, who lives in Celestic Town, will tell the player that in ancient times, people apparently met with Dialga and Palkia, by having the Adamant and Lustrous Orbs. Returning to Spear Pillar with these items, the player will be able to battle with and hopefully capture Dialga and Palkia.
Q4: And the final question, how do you get the Lucky Egg?
Chansey has the Lucky Egg, and to get the egg you can catch many Chansey's, see if any have the egg, and then take it. The second option is to steal it with Thief or Covet.
And those are some helpful tips and tricks for: Pokemon Platinum. Expect updates in the future!