I think of a gap up as the bull flag that it resembles, and sometimes I play it that way if I see a classic consolidation in the works. It seems to work at least as well, if not better, than expecting a gapped stock to go back and "fill the gap" with price action. Also depends a lot on the trend before end of day. And VOLUME. If 200 shares trade in 5 minutes or if 2500 shares trade in 5 minutes makes a difference.So if anything, try and build a strategy around gap continuation?
I don't play a gapper until I have seen 3 or 4 5-minute candles after the opening bell. Premarket trading can be totally divorced from open market trading. Also the spread. A big spread to me is a stay away signal and after the bell that 60 cent spreader might be down to 1c or 2c.
