In order to minimise the time required for a group of survivors to locate a potential bandit threat, I'm going to try to use the following system for reporting contacts, lifted from the ShackTactical ArmA2 TT&P Guide.

Note this only applies to player contacts. Zed you just still call out the same way.

1) Call "Contact" to alert your group that you've spotted players. The sooner everyone knows about it the sooner they can act.
2) Give brief directional information to Orient the group to the contact. Compass directions are prefered, particularly in degrees, but since speed is important, and compasses aren't always available, calling out a relative direction such as "front" can be functional, so long as everyone knows which way front is.
3) Describe the type and number of contacts, briefly. For now, bandit status might be useful, but not likely to be in the near future. Weapon types also useful, if visible.
4) Finally, once all the basics are covered, you can provice any additional information that might be helpful.

Examples:
"Contact, North-West, survivor, in the second story window of the brown-roofed white-walled building at the crossroads."

"Contact, bearing zero eight five, three men, prone behind the rise 200 meters to our front, looking the other way. "

"Contact front! One bandit, one survivor, sniping from the firestation tower due West, 400 meters. I don't think they've seen us yet."

Just remember, CODE:
Contact!
Orient
Describe
Elaborate