You create a new file called <MAPNAME>.cfg, obviously, replace <MAPNAME> with the name of the map, i.e. pl_badwater.cfg. In that file you cna place all the cavrs that need to be changed for that map.
Keep in mind if the next map doesn't change these cvars, they will stay the same.
And blesser, most of the questions you seem to ask are probably best off asked as the SRCDS forums :
http://forums.srcds.com/