The talking heads on crapvision call the time between 3 P.M. and 4 P.M. the most important hour of the day. It isn't for traders. The most important hour is the first one. But the last hour does serve a purpose.
After the market closes bring up an hourly chart of the previous session for DIA, SPY and QQQQ. If the last hour prints a doji or a white candle the next day, barring catastrophic news, will probably open higher.