They should, however, be followed for any new code that is written. Portability - refers to how easily the program can be ported to new computational platforms. They impact all three of the items listed above - maintainability, portability, and efficiency. Try to minimize the amount of C code, however.
Organization Write modular code.
In general, put each subprogram in a separate file, using the subprogram name as the file name, with a .f extension. Group related files in a single directory, but don't go overboard. Names of files and directories should reflect their purpose. Common Blocks Don't use blank common. Put all common blocks in include files, one per file, using the common block name as the file name, with a .inc extension.