how to talk in three lines, in cell phones (or regular, wireless)?

Answer 1

For regular, make your first call, hit flash, make second call and wait for answer, hit flash again and all 3 parties are connected.

On cell phones, it depends on the network/phone. On GSM, you usually make the first call, go into the menu, pick new call, once connected go back into the menu and pick "conference" or "join calls" and all three parties would be connected.