Bush Tucker Guy,
As mentioned before, the easiest way is the overwing exits!
Also, (with regards to the QF fleet):
OGA-OGV: -338's, 2 overwing exits and GE engines (white cowlings).
ZXA-ZXG: -336's, 2 main doors fwd of the wing, 4 doors in total each side with the 3rd being an emergency exit only. Rolls Royce engines (grey cowlings). These ones came from BA, hence the differences.
EAJ-EAQ: -238's, 1 overwing exit, P&W engines (white cowlings). And the fuselage looks unnaturally short compared with the tail/wing size!
Generally most 763's around the world have the 2 o/wing exits instead of the 4 doors.
Hope it helps!
