This post explains general steps to make a simple A Simple Outdoor Map in Counter Strike 1.6 and Condition Zero in Counter Strike 1.6 and Condition Zero.
You can learn the step by step instructions at Superjer
Map Installation Intructions:
Copy cstrike to installation folder of Counter Strike 1.6 or Condition Zero.
How to make this map:
Use Valve Hammer Editor or Quark (Quake Army Knife)
Required textures: halflife.wad
Required entities: info_player_start (CT Spawn)
info_player_deathmatch (T Spawn)
light_environment (lighting for outdoor area)
Addition: ‘sky’-textured brush.
Not sealing the map using sky-textured brush will cause leak in the map. As a result, hall of mirrors will appear on the leaky part.
See the difference between outdoor.rmf and outdoor-leak.rmf