Different airlines have different standards of preflight briefing, but the rapidly growing airline thats based out of Dubai has a preflight briefing as follows:
10-15 minutes long.
Document check: all crew have passports, valid licence etc... fit for work.
Covers:
Flight details (crew, timings, loads, services, paperwork etc...)
Safety: quick brief on emergency procedures, including safety, security and medical. These days generally done with asking each crew individual questions to ensure they are up to speed.
Other aspects of flight that may need to be addressed (how the seniors may want service conducted, particular points to look out for)
Briefing by flight deck: weather report, flight plan+ actual flying time, safety/security from their POV.
Allocation of positions.
Mad dash out the door for a final cigarette before getting on the aircraft.