You will need
- - access to the Internet;
- - information about the deceased.
Gather as much information about the dead relative. Except its full name, you may need his date and place of birth, the name of the district where he was drafted into the army, a number of military unit in which he served, or at least branch of service, time of leaving the service, and death or disappearance.
Start your search with online resources. To search for the victims in the great Patriotic war in the Soviet time was created a "Memory Book". In two thousand years it was digitized and now it is possible via the website of "memorial" - http://obd-memorial.ru.
In the menu "Search", specify the name, surname and patronymic of cousin, and, if known, date and place of birth. The system will give you a list of names, among which you will be able to find the right person. From the information card you will be able to know the date and place of death, cause of death, and in some cases place of burial. There are similar online lists and killed in local conflicts. For example, information about the victims of the war in Afghanistan can be found on the website http://afgan.ru/mortirolog.htm
If the Internet does not have all the answers to your questions, contact the archive, for example, in the Russian state military archive - http://www.rusarchives.ru/federal/rgva/index.shtml There at your request, you will be able to provide information about a particular relative and information about the place of burial, if known. The request can be passed as by personally visiting the institutions and email. But be prepared that the results will have to wait quite a long time.
To search for the victims in the great Patriotic war contact one of the search teams, for example, the one represented on the website http://www.poisk-pobeda.ru/index.php. These organizations consist of groups of enthusiasts, conducting excavations in the battlefields and engaged in the reburial and identification of fallen soldiers. Perhaps among the recovered victims of the war will be a wanted relative.