Here is a very simple guide to how the new DRS wings will be used this weekend in Australia.
DRS can only be used if car A is within a second of car B at the timing beam on the run in to Turn 14, which is noted by a line across the track.
Between Turn 14 and the beginning of the overtaking / activation zone at Turn 16, the driver of car A will be notified that he can use the DRS in the overtaking zone.
If car A is within a second of car B at the timing zone, but driver B pulls into the pits at the end of the lap, the driver of car A can still use DRS in the overtaking zone.
If car A has been lapped by the driver of car B, but car A is still within a second of car B at the timing zone, the driver of car A can use the DRS in the overtaking zone.
If the track is declared wet, the DRS cannot be used.
DRS can be used at any point around the track in all practice sessions (including qualifying) unless otherwise stated by race control.
For reference, the detection point for the gap between drivers is 13 metres before Turn 14, and the activation point for DRS is on turn in for Turn 16, 867 metres before Turn 1.