How you can trade Pokemon in Pokemon Crystal?

In Pokemon crystal, a trade can be accomplished through the following steps.

1) Have two of any of the following: Game Boy Advance, Game Boy Advance SP, Game Boy Color

2) Other than your Pokemon crystal, have a copy of any of the of the following: Pokemon Gold, Pokemon Silver, or Pokemon Crystal

3) Insert the games into their respective systems

4) Upon entering the game, go into the Pokemon center and head to the top floor.

5) Hook up both game systems with a Gameboy Link Cable

6) Find the receptionist who will allow you to enter the "Cable Club Trade Center"

7) Once you are both inside, you will be able to select Pokemon to trade.