At first, people used air as a medium of transmission. Later, people needed a harder form of transmission. In that, people began to use rocks and such to write things down. Later on, they used caves as they had moist walls, in that, they were easy to put script on. They would write on higher areas of the walls as to prevent any displacement of the written text. The cheif weakness of a cave was that one could not transport the text. In that, the nomadic people could not bring the text with them.
Later, stone became the next medium. It offered mobility, but it does have its drawbacks. The rock was very difficult to work with, in that it would be difficult to carve and had a very little room for error.
Clay later became the new medium. Though, some still called it "stone." The clay was formed into tablets in which they would cuneiform(~2000BC); this was used with single shape chaacters. It was different from Chinese script in that it didn't have forming lines, rather, it had single lines. The wet clay was used to write on, after that, it was dried or heated. In the socities that used clay, they typically lived around bodies of water. They were able to make uniform masses of these clay tablets in that the clay was much easier to work with than stone. Clay itself had its drawbacks as well, in that it was liable to breaking and losing shape.
Later on as inks/dyes were developed, socities began using animal skins. Animal skins were much lighter than that of clay tablets and stone tablets. The animal skin was very difficult to fabricate, in that it was very labour intensive. It also needed some maintenance. The skin was also somewhat scarce in that not very many animals were used were not often slaughtered.
Later, papyus was used to write on. It was a primitive paper -- made primarily of smashed reeds that were laid in bi-directionally. Low humidity countries used this technique.