How do you put bluetooth in discoverable mode?

Bluetooth devices, when in discoverable mode, are able to be seen ( discovered ) by other bluetooth devices. If two phones connect, the phone that is trying to establish the initial connection, must be looking for a phone that is "discoverable" otherwise it will not see it. Once the connection is saved, discoverable mode is no longer necessary, as the phones already know each other. This is only necessary during an initial link.