Here are some ways to obtain rare items in Pokemon Emerald:
* Berry Master Contest: Winning the Berry Master Contest in the Battle Frontier will reward you with a Star Piece. However, this is not available in the original Pokemon Emerald game, but may be available in ROM hacks or modified versions.
* Trading: You can obtain rare items through trading with other players, including Star Pieces.
* Cheating: Some players use game-modifying tools to obtain items that they cannot normally get. This is considered cheating and may go against the rules of online multiplayer games.
It's important to note that obtaining Star Pieces in Pokemon Emerald is not possible through normal gameplay. If you're looking for a way to get Star Pieces, you may want to consider playing a later game in the Pokemon series.