Important stuff in preparation for technical interview:
1.If you see anyone make a mistake, correct it even if you may later look like a knob.
2.If interviewer tries to lead you down the expeditious route rather than the safe one stop him in his tracks asap.
3.Know how Vortex Wake works.
4.Know Airway dimensions.
5.Brush up on aircraft recognition skills.
6.Know how flights over the North Atlantic operate (track structure, effect of weather on route selection, no radar over the Atlantic etc).
7.Know that an aircraft will take off into wind, not with the wind coming from behind it.
8.And finally, they'll probably ask you a distance/speed/ time question e.g. if an aircraft is travelling at 420 knots how long will it take to travel 140 miles?
(You get a pen and paper and are expected to do this in about 10-20 seconds).