I'm pretty sure everybody is working hard on their maps, but in case somebody is still having difficulty setting up their hammer/haven't touched Half-Life in a long time...
Downloads:
Hammer 3.5
Half-Life FGD w/ model support
GCFScape
Zoner's Half-Life Tools
Hammer 3.5
The latest version of Hammer, although it's still a beta (for how long?), it is recommended to use. This is only an executable, so make sure you have 3.4 installed first (which I assume you do).
Half-Life FGD
This version of the FGD supports rendering models in the 3D viewport, which is very helpful. But in order to set up model support, you need to do a bit more (covered below)
GCFScape
It's basically PAK explorer. You need to extract the models folder from the GCF to .../half-life/valve folder, because Hammer can't read files directly from the GCF. Make sure you extract the halflife.wad as well.
Zoner's Half-Life Tools (ZHLT)
Use these compiling tools instead of the ones that come with Hammer 3.4. Extract these to your Hammer directory, or somewhere appropriate.
Setting up Hammer
Tools > Options > Game Configurations tab
Edit button > Add 'HLDM' > Add the half-life.fgd
Default point/solid entities could be anything, it's up to you. I use info_player_deathmatch and func_wall respectively.
Game executable dir: (where your hl.exe is located)
...\Steam\steamapps\your_name\half-life
Mod dir: (it's not really a mod, so choose the default valve folder)
...\Steam\steamapps\your_name\half-life\valve
Game dir: (no matter what mod you're mapping for, this must point to the valve folder)
...\Steam\steamapps\your_name\half-life\valve
RMF dir: (optional, I don't bother with this)
Onto the compiling tools
Inside the Build Programs tab, pick HLDM (or whatever you named it) in the drop list.
All of them are self explanatory. Game executable must point to hl.exe, BSP CSG etc. point to the ZHLT compiling tools.
Edit:
