Since I saw quite a few people here recently acquired the wonderful S.T.A.L.K.E.R games in the steam summer sales, I thought I'd write this quick guide to get you into the zone with minimal hassle. So, rookie stalkers read on, veterans, skip to the end for a hardcore mod recommendation and some upcoming projects to watch!
I would like to preface this by saying there's nothing wrong with playing the game in its vanilla state: However, you're going to miss out on a lot of the community’s efforts to further polish these games.
Each title (Soc, CS, CoP) has a Complete mod produced by artistpavel. These are the mods you'll want to use for your first playthroughs, as they bugfix, improve graphics, AI etc without harshly tinkering with how the game was meant to be played. The changelist for each game is quite impressive, so you'll want to read them from the artists blog, which can be found here. Alternatively, you can find the mods hosted on ModDB.
Each mod has an .exe installer, which should work without a hitch, however if you encounter problems you can downloaded the zipped package and do it manually. This will probably involve an extra step for Steam users, but should still be quite straightforward. If you have to do it this way, google will point you in the right direction.
Want to play with the game files yourself?
In your install dir, you will have a resources folder (Unless you're working with SoC). This resource folder hosts the .db files you'll need to extract. To do this simply you can use this tool. After you extract the databases you'll have access to all the assets. In order for the game to read the modified files over the files stored in the .db files, two things will need to be done. First of all, the modified files will need to be inside a folder called 'gamedata' within your game directory (maintaining the file structure from the extracted .db's - ie if you retextured the VSS diffuse map your new file would be located in ~\S.T.A.L.K.E.R. - Call of Pripyat\gamedata\textures\wpn\wpn_vss.dds)
Secondly, you'll need to tell the game to read from the gamedate folder. This is a simple config change - open the fsgame.ltx file within your game directory with your favourite text editor and edit the $game_data$ line to read true, like so:
$game_data$ = true| true| $fs_root$| gamedata\
Simple. If you've installed a mod via an exe it's almost guaranteed this change has been done for you.
Other mods and upcoming projects:
For the STALKER veterans, here is a mod that might interest you: MISERY for Call of Pripyat. This mod greatly increases the difficulty of the game, and makes it harder to survive, earn money, etc. it also adds new content, graphics/weather improvements, etc. You can find the mod and track its progress from its ModDB page. It's great mod and the blowouts are phenomenal, but you might want to wait for version 2. Personally I found the difficulty increases only hurt early on in the game, I was still able to get 100,00k roubles + good gear before even going to Pripyat. Additionally the sprinting penalties inflicted by this mod are beyond just sadistic, When playing the 'Sniper" class you're limited to 30kg carry weight (which can of course be increased through suit modifications / artifacts) but you don't regen stamina while walking. Since this is incredibly silly, here's a link how to fix it. Also, this mod is quite demanding on your rig and the load times are significantly increased, so you've been warned.
A long time in development is the Lost Alpha mod for Soc, with a release scheduled for September, just in time for my birthday. This mod will attempt to bring back the content originally planned for STALKER, with the team reworking many of the maps and recreating unfinished maps seen only in old promotional material. It's got a lot of stalker fans excited, so head over to their ModDB page to see what the hype is all about.
Finally, a rather ambitious (and by nature unpolished) mod for SoC: Priboi story. This mod is as close to a total conversion as you'll get - along with the usual content additions (weapons, items etc) you get a new storyline to experience. I believe I played the earlier version (1.0) of this mod which was quite unspecific on what you had to do, which is where walkthroughs came in handy. If they haven't changed this or I was mistaken and did play the current (1.1) release, then there's no shame in using this walkthrough guide - it's not always clear what you're meant to be doing.
That's all for now, if you've got any other STALKER mods or recommendations, share them in the comments, and happy hunting stalker!