Life hacks from a male daily commuter and a keen observer in Delhi Metro.
Travelling in an Indian metro city for daily can be a daunting task for many. After travelling in Delhi Metro for over 4 years helped in observe and develop certain tricks and hacks to find a comfortable seat in a sea of crowds.

Always get an 8 coach metro and preferably get into the 7th one. More seats. More Possibilities.
Stand 2 meters away from the end of the 6th coach. The metro door will open right in front of you.
Take a quick lookout in the coach: There are four corners in a coach; forget the 2 seats which are reserved mostly for elderly/ differently-abled. Out of those four corners, one corner- 2 seats will be for Females and other corner-2 seats for elderly/ differently-abled.Â
Now omitting the said 2 corners, we have perfectly probable 2 corners for consideration. These two corners have the highest probability of you getting a seat.Â
Time for facial and behavior surveillance. Out of the people sitting in the considered corners, always check for people for who are on the edge of their seats; who seems anxious and looking at the metro display maps or looking out of their phones. People who relaxed and deeply seated are probably not getting up soon.
Once you have identified the anxious ones, stand just right in front of that person sitting and the person next to him. Cover two person at a time :)
All things are based on probable situations.
Otherwise, take any seat you find.