While you and your family/friends may be able to easily TELL that your loved one is dead, remember that we live in a world highly affected by documentitis and it is therefore prudent to organise a document declaring death.
I say first 15 minutes because bodies tend to decompose pretty steadily and you may want to begin preserving your loved one’s body in a refrigeration unit as soon as possible. I also say first 15 minutes because when you realise a person is dead, emotions run high and /or a complete numb shock may take over and you just sometimes need a few minutes to grieve.
When the doctor arrives, he/she will need to check the person before pronouncing them as dead. Once the person is declared dead, the doctor will proceed to write out a statement on the letterhead. You may be required to supply details such as name of the dead person, their date of birth, name of parents and/or spouse, house address, approximate time of death and nature of illness (if any). You may not necessarily know all these details - that's fine, just do your best to give as much correct information as possible.
In India, this statement of death given by the doctor is one of the things you will be required to submit when applying for a formal death certificate, which is issued by municipal authorities. Note that if your loved one passes away in a hospital, the hospital will issue a death summary that you should submit. I will write a separate post explaining the procedure for obtaining a formal death certificate.
I hope this has helped you. I would be happy to edit and update this post - let me know in the comments section if I have missed out any crucial information.