* Edit the help file skeletons in 'man', possibly combining help files
  for multiple functions.
* Put any C/C++/Fortran code in 'src'.
* If you have compiled code, add a .First.lib() function in 'R' to load
  the shared library.
* Run R CMD build to build the package tarball.
* Run R CMD check to check the package tarball.

Read "Writing R Extensions" for more information.