Howto create software package in Unix/Linux?

An alternative to the hard to understand GNU/Autools is CMake.

http://www.cmake.org/cmake/help/examples.html

e.g. KDE is using it.

Look into the GNU autoconf/automake toolchain. Here's a free tutorial/book.

In the old days, this process was done by hand. Each Makefile was written by hand (the file make uses as a sort of script). This became problematic when it came to portability, and so the configure script was made. The ./configure script was written by hand for each project as well. Eventually this was automated by GNU with their autotools package. This consists of autoconf, automake, and a few others. While alternatives exist, particularly for make, autotools is most widely used. ...At least on GNU/Linux systems. Alternatives include the already mentioned CMake, Boost.Build, Boost.Jam, SCons, and more.