For FTSE an DAX the opening of the DJIA
For the SPI. The HSI/Nikkei/China
Individual Reversal Bars and blow off patterns.
News events--big ones.
Strong support or resistance supported by blow off volume coming into it.
Combinations of the above.
According to the moneyclock, the period from 4:00-5:00 am EST has been a bullish bias for the last few weeks....I'm assuming this is just a simple algorithm that buys 1 car at the open of each hour and closes the trade at the end, then ranks by win/loss and profitability to give an idea of any statistical biases for time of the day, over the past 14 days, which is the max look back period.