You should always perform a "trailhead check" (aka a "transceiver function test") before heading into avalanche terrain. This test ensures that your avalanche transceivers can transmit and receive, have sufficient batteries, and that everyone knows how to switch between search and send.
Everyone should turn on their transceivers and verbalize their battery level. You can read more about transceiver batteries, but in general you should replace them when they fall below 50%.
This is a good time to confirm that, in the event of a multiple burial, everyone knows how to turn off their partners' transceivers.
One person should change to transmit and the others should change to search. (If there is a group of people, it is helpful if the people who are searching form a circle around the person who is transmitting.)
The people who are searching should tip their transceivers down slightly so they, and the person who is transmitting, can see their transceiver's screen.
The one person who is transmitting should move her transceiver toward each searching transceiver, one transceiver at a time, while watching the searching transceiver's screen to ensure that the displayed distance decreases. (The displayed distance on most transceivers will decrease to 0.1 meters. A few transceivers will only decrease to 0.3 meters.)
After confirming that all the transceivers are receiving the signal, the people who are searching should switch to transmit (aka send) and properly stow their transceivers.
The one person who was transmitting should now switch to search mode and, one at a time, move her transceiver near each of the transmitting beacons to confirm that everyone is transmitting and that the distance displayed on her transceiver decreases as it nears each of the transmitting beacons.
The person who is searching should then switch her transceiver to transmit and stow it. It is critical that this person does not mistakenly turn off her transceiver, because it won't get checked again.
Some avalanche transceivers will "lock" onto the strongest signal and won't switch to the closest transceiver during this test. If your transceiver has a "group check" mode (almost all do), you should enable it when checking to see whether your partner's transceiver is transmitting.
Although the above process looks complicated when each step is spelled out, it is an efficient way to check that each avalanche transceiver can transmit and receive. Starting with one person transmitting, and ending with all but one transceiver transmitting and stowed, is a sound approach.
At least annually, you should do a more thorough test of your (and your partner's) transceiver. The above function test, albeit efficient and appropriate, does not test other important features, such as the distance at which your transceiver can receive a signal (although the reception range will get tested when you practice).
The following video, courtesy of Backcountry Access, demonstrates a slightly more thorough trailhead check.
