In most avalanche situations, any defensive action is very difficult. Movement relative to the debris is often impossible.
However, some of the following may be useful:
If you witness an avalanche burial:
This series of videos from Glenmore Lodge examines techniques for searching with avalanche transceiver and probes and for digging for different burial depths.
The avalanche probe is the main tool used in searching avalanche debris for buried victims. This video shows how a search should be conducted.
It's vital that a buried avalanche victim is uncovered as quickly as possible. This video shows where to start digging when your probe reveals a casualty close to the surface, and explains how to dig for maximum speed and efficiency.
If the probe shows the casualty is deeply buried, you should adopt a different approach to avoid disturbing any air pockets and to reach the person as quickly as possible.
Two people can make lighter work of digging out a casualty, but only if they work together efficiently. This video shows how to dig as a team for faster results.