The easiest way is this:
Edit: Here's the text from the manual. Any use of bold, numbers, and bullets are from the actual manual text.
Wii Operations Manual - System Setup, page 20
ONE TIME MODE - This mode allows you to temporarily use your remote on
a console other than your own or to
use a friends remote on your console.
It does not delete the Standard Mode setting stored in the remote.
Wii Operations Manual - System Setup, page 21
One Time Mode Synchronization
NOTE: This mode temporarily removes
the Standard Mode synchronization
setup for all remotes until the power
of the Wii console is turned off. When
the power is turned on again, the
Standard Mode settings will return.
Press the HOME Button on a remote that is synchronized with the console.
Select the Wii Remote Settings option from the Home Button menu, then
select the Reconnect option.
Press the 1 and 2 Buttons simultaneously on the remote that you
want to synchronize with the console.
The order in which you synchronize remotes will set the player order for
The Player LEDs will blink during the syncing process. When the
blinking stops, the connection is
complete.See diagram at right for description of what the blinking indicates.
Next to said diagram:
During the syncing process, the number of LEDs that blink will show the battery life of the remote that is being synchronized.
After the syncing process, LED that is lit shows the player number for that remote.
NOTE: One Time Mode synchronization is temporary. The Wii Remote will lose this synchronization under the following conditions:
- When your turn off the console by pressing the Power Button on either the remote or the console.
- When starting up a game or Channel from the Wii Menu.
- When returning to the Wii Menu after exiting from a game or Channel.
- When you select Reset on the HOME Menu Screen.
- When you press the Reset button on the front of the console.