Hello Ravinder,
When I start a pair trade I first take that positon which is go in the extrime, I men that say if the nifty index suddenly raise fast than I will sell CE first because I think that the nifty index will not raise more from there. So I think that the nifty index will 1) not go up raise more OR 2) It remain there only.
So if it remain there for some time and not correct down side I will then sell PE in after some time. And many time like my thinking, the nifty index will corract for some points and the price of PE will became more, so than after this small correction in nifty index I will than sell PE. I do the shame thing if the nifty index fall down side fast, than I will sell PE first and then after sometime, if the nifty index baunce than I sell CE after some time. If the niffy index do not baunce than I immedatly sell CE and so I has a pair positon.
I more do sell options pair because I earn time decae points by sitting with the positon. But I also do buy option pair some time, if I thing that there nifty index will go in one directon for more points.
Thank you and best of luck for tomorrow.