Welcome to the Communication Important Acronyms Category
ATMIST is used for casualty handover to an ambulance crew:
A (Alpha) - Age of the MisPer/casualty

T (Tango) - Time of the incident/arrival

M (Mike) - Mechanism of injury

I (India) - Injuries

S (Sierra) - Vital signs

T (Tango) - Treatment given
IIMARCQ is used as a recognised method for briefing:
I (India) - Information (details of the MisPer)

I (India) - Intention (what you intend to do and why)

M (Mike) - Method (the methods that you will employ)

A (Alpha) - Admin (make sure all paperwork has been completed and all equipment is ready)

R (Romeo) - Risk (are there any known hazards and are team members aware of the risks?)

C (Charlie) - Communication (make sure phone numbers are known and a radio channel has been configured)

Q (Quebec) - Questions (ask questions yourself and allow people to ask questions back to ensure that everybody understands everything they need to)
WARTHOG is used for giving team situations reports:
W (Whiskey) - Where/Grid reference

A (Alpha) - Achieved % covered of the search area

R (Romeo) - Remaining time required to complete

T (Tango) - Terrain (a brief description)

H (Hotel) - Help; are you in need of any resources?

O (Oscar) - Other issues, such as team welfare

G (Golf) - Goodbye
Other acronyms can be found in the other Important Acronyms Categories:
r5c1
Medical
r7c3
Drones