The market pushes me to short at least one of the high flying big stocks at the time when they flash some climax reversals. Other than that I rarely short the initial break off the highs but rather wait for reaction rallies into resistance in the former leaders which had the most severe, high volume breaks off the highs. Regarding ETFs I only go long $UVXY sometimes.
This sums up my approach to the short side which I adopted from Bill O'Neil and Gil Morales.