One way to go about making a map:
1. Come up with an idea for what you want to map.
2. read up tutorials from twhl and others: google search half-life mapping and/or cs mapping, and you will find tons of sites and tutorials.
3. download/install/configure Valve Hammer Editor. reference the
tutorial Huntey aptly posted.
3a. Reference the forums for any configuration/setup questions
4. Build and compile your map.
4a. Search the forums and
this site for questions/errors regarding your compile.
If i could give you one piece of advice as a new mapper (besides reading up on tutorials and the forums) is to compile your map often. Too often, i see mappers build the gigantic "map of their dreams" without trying to compile it even once during the build.
The result is an uncompilable map with so many errors, it's basically uncompilable. After you get your first "box" with an info_player_start and a light to compile and play, i would recommend compiling about every hour of editing time, or even less at the beginning.
Doing this will make it MUCH EASIER to troubleshoot problems with your first map...
Sorry for the long-winded response.. Hope it helps!
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