My model for saving a remnant of the human race is the creation of Sanctuary. For centuries sanctuaries have been centers of refuge in time of trouble. Scientists, mathematicians, writers, artisans of all trades will build 40 different refuges able to withstand long periods of time after nuclear apocalypse. Within these centers they preserved not only human life, but also plants, animals and knowledge.
The original inhabitants of each Sanctuary numbered 1000, representing 20 distinct ethnici groups While some centers were populated by favoritism, a few were more insightful in their selection methods. These decided to include a cross section of society as a whole, from the rich and powerful to the meek and talented. This increased their chances of success tenfold. The centers which found themselves full of scientists soon found themselves drawing straws to complete menial tasks.
All centers were outfitted with water and air purification systems, controlled farmland, animal habitats, living space and most important, computer centers outfitted with specialty constructed generators. Alternative forms of communication between centers was created, knowing that satellite reception and transmission would be almost nil after the bombs fell. The locations were carefully selected based on geographic stability.
Over the centuries, individual labels such as 'scientist' or 'farmer' disappeared and experts in all fields began to be called 'Druids' after the legendary ancient priests. Men studied all areas of knowledge instead of specializing in one. Things from before the destruction were pondered and debated upon to see if they would contribute to society or lead men down the road to ruin again.
After the air was bearable again and humans returned to the surface for a permanent residence, the Sanctuaries slowly began to fall into disrepair. Most have been lost to time but a few remain. Only the Central Plains Sanctuary remains intact both in structure and in contents. For that reason the exact location of the Sanctuary has been kept and protected by the Central Plains Nomads, direct descendants of the scientists who became Druids after they decided to save the world.