Your Linux distribution probably includes more than one CD-ROM chock full of RPMs. Each of these RPMs has a spec file. You can examine these spec files and see how others choose to build their RPMs. Rather than starting from scratch, you can copy declarations from these spec files into your spec file.

Not all these packages were made smartly. Some spec files, as you will see, are a large mess. Obviously, don’t copy these. Look for clean spec files with clear directives.