The Selfdocbook is held together by magic sed glue, which is activated by some rules in the Makefile in the appendix called DocBook SGML source. So, in order to build the Selfdocbook you will need make and sed (and also fold). Note that sed and fold won't be necessary for all SGML projects, but using a Makefile is usually a good idea.
To have a functioning SGML environment, you will need to have various programs installed. On a Red Hat Linux 7.1 system, the sgml-common, openjade, jadetex, docbook-style-dsssl, perl-SGMLSpm, and docbook-utils packages should be installed, as well as the packages whose names begin with docbook-dtd.
I use an emacs package called psgml for editing SGML documents. The keybindings I find most useful are:
Tab indents the current element to a level appropriate to its nesting depth.
Control + C Control + T lists the valid tags for the current element.
Control + C / closes the current element.