How do you trade Pokemon in Pokemon HeartGold?

On the "upper level" of the Pokemon center, there should be three people behind desk counters (that look like nurses). The center one directs you to the union room, which pretty much where you go with your friend to trade.

1. Both you and your friend bring the Pokemon you want to trade in your party
2. talk to the lady in the center.
3. say yes to everything and save (blah blah blah)
4. go into the union room
5. Your character should be represented as an ingame CPU sprite (i.e. cool trainer, breeder, etc)
6. One of you talk to the other person's sprite (Either you talk to your friend or he talks to you. If you both try to talk to each other at once, it will lag severely, and the actions will be automatically canceled)
7. Who ever started the conversation selects "trade", and the trade begins


If you meant trading by the GTS...
1. Go to golden rod city
2. There should be a small bridge.. .cross the bridge to arrive at the GTS building
3. talk to the guy in blue with the fedora hat, and say yes to everything.. blah blah blah, save game... blah blah blah, connect to Nintendo WFC
4. Go into the mysterious room. You can now search the Pokemon to trade by using an alphabetized selection of Pokemon that you have seen