Some random thoughts from my observations.
During the overnight session (from a US perspective) it is the European & Asian markets driving things. Why not watch these rather than the overnight session? Really you are using a 'proxy' for these other markets if you look at the US electronic session. Having said that it is useful to see what levels are established overnight and how they hold next day. Nowadays Europe is every bit as 'powerful' at driving things around. The last few days European markets have been pushing through significant levels before the US opens. Once the US day session starts obviously it opens at this lower level.
Talking of useful levels I have found daily weekly and even monthly charts hugely useful in seeing what has been 'gapped' through. Try looking at a weekly chart, really illuminating. I'll try and post a
DAX one for those that don't have Europe data. Its been hugely 'technical'.
Richard Ney has lots to say about gaps and detecting what's real and what's not (though he was talking largely about the NYSE). He alleges the clue is in the predominant trend the previous day, the trend for the last part of the previous day, and the open.
Personally I think support is support and resistance is resistance. When it blows it blows! I am not sure if there is anything to gain by analysing when it blows (i.e. overnight so leaving a 'gap'). I think markets really are becoming truly Global and truly 24 hours though empirically stuff seems to happen less often Asian peak.
Dog, I'd be interested in how you trade differently when a market opens in balance or 'gapped' out of balance?
Cheers.