What I do is,
I add more when stock breaks in upper trendline and make an exit when it breaks its lower trendline.
Example One I already gave- Reliance a perfect down trend.
Mcdowell and ITC are example for bulls,also keep an eye on Global tele which has broken its upper trendline which was at 111.80(I use bse quotes btw).T can be anywhere fm 144 to 167,I shall exit half at 124 for safety to bring my purchase cost down.