Instructions
Connect two Game Boys using a Nintendo Link Cable.
Travel to any Pokemon Center, located in each city, on both Game Boys.
Enter the Pokemon Center and walk to the second floor on both Game Boys.
Speak to the Cable Club Time Capsule woman using the Game Boy running "Pokemon Gold."
Speak to the Trade Club woman using the Game Boy running "Pokemon Red."
Save your game on both Game Boys when prompted. Press "A" on both Game Boys when standing next to the table.
Select any Pokemon from the Game Boy running "Pokemon Red." Select a Pokemon on "Heart Gold" that was originally in "Pokemon Red" and knows only moves that were available in the game as well. Otherwise, the trade will not work.
Select "Trade." The Pokemon will now be traded from "Pokemon Red" to "Gold."