How to actually do death contemplation?

How to do death contemplation ? it seems i really dont care about dying that much how long can i do it ? is there a formal technique to do it ? cause just thinking about it dosnt seem to have no effect at all i do seem to care about others who die though but not on myself - and even on others i care much more about them being ill and suffer than them dying so any tips you have to add to make this more effective would be great and just to make it clear : i want to do this to get a sense of urgency so i will meditate more so i will get chanda