If you or your belongings are seriously injured then you can ask for 3/4th of the amount which you are insured for. For example if you have a policy of 10 million USD you can claim up to 7. 5 million USD. For that ensure you have all the proof. Best of Luck.
You need to ask for a reasonable amount which actually covers your expenses and some for pain and suffering if you have experienced any of that. You do not want to ask for too much or they will put you off.
It depends on what you are trying to get paid. Your question is too vague, let's say it is for an injury with time lost from work. You need to show how much your medical bills were and how much money you lost from time off work.
You are walking a thin line. Demand what is fair and honest. Be sure to list what was damaged and how much you are demanding in compensation. Asking for outrageous demands may put your letter in the trash.
We can't say that approximately but it is based upon the type of insurance whether it is Life or General, Period or Tenure of Insurance, Sum Assured you are demanding for the Insurance.