I only really do Landscapes so not really relevant to your question Heinz - but yes, I do make in-depth preparations if I'm planning a particular shot/shoot. Google Earth, Sunrise/Sunset calculator, tide tables, weather forecasts etc etc etc - it's nice to be able to get into position for the planned shot in plenty of time and watch the anticipated show unfold.
If I'm getting up at 4am, I want to maximise the potential so as to make it worthwhile - just a shame the biggest variable is the British weather
Cheers
Andy