For pretty thorough instructions on how to set up a DocBook working environment see the INSTALL document by Eric Bischoff, the KDE documentation coordinator, in the kdesdk/ksgmltools package.
Nevertheless, it can be difficult on some systems, to get all the components of such an DocBook environment (SGML parser, DTD, stylesheets etc.) working together in a way that results in usable output. If you experience such difficulties with your system, please contact Eric immediately and tell him about your exact problem with as much detail as possible. Often it's just a few variables that need to be set or accommodated. But the more the SGML folks at KDE know about possible problems the better will everything run on all systems in the end, of course.
Apart from the programs that form a working DocBook environment you are going to need some tools that allow the production of screenshots in PNG format. Due to licensing problems, KDE like many other free projects had to give up on GIF format for their graphics.