General Files in Res File
Comments
Preface comments with // in front of the line. Most people put a comment line on the top with the name of the map and maybe mappers name or version info.
Map (.bsp) Files
Many server admins believe that the map file must be referenced in the res file. I have found this unnecessary as half-life already knows this info. If you put the map name in, I have found that it usually requires the player to download the map twice.
Configuration (.cfg) Files
As with the bsp files it is not necessary to put the .cfg files in the res file. However if you want players to get the .cfg files so that they can play the map as a listenerver or lan, then include the .cfg files. The two type of .cfg files you would deal with here are the mapname.cfg and the mapname_skl.cfg files.
Res Files (.res)
Again, not necessary unless you want to have the player get enough files to be able host a listenserver or lan with your map.
You should include all the models and sounds, etc. that are need to run the map, please do not include any models from eariler maps in your series. Your map should be able to run on it's own with the files in your map package.