This is honestly more of an article than a tutorial, but thats alright. This should help all you who are new to the mapping world and give you a basic understanding of what defines a good map from a crap map. It won't tell you how to create a great map, just what you need to create one. In all honesty, this is probably more of a rant after seeing yet another newbie pimp a map they say is awesome, and a great map, but really, is horribly unimagionitive and badly made, and not fun to play for more than 30 seconds.
Ok well lets get down to it:
1. Brushwork
2. Textures: choice and alignment
3. Lighting
4. Layouts
5. Details
5. Misc.
Well, thats all I have as of now, but I garentee I'll have plenty of stuff to add to this. On a side note, I have nothing against fy_ or dm_ maps, there are definately some quality ones out there. What I don't like to see is people pimping maps that they have mayb e worked on for a few hours, or maybe a day or two, and it shows with its poor quality. If you don't know what to do to your map, take a break for a while and do something esle. After a while, ideas will start coming back to you, and then work on your map some more. My map, cs_interrogation was in the works for 3 months or even longer (my memory seems to be failing me), and it still could use polishing. Please do not rush your maps. Invest time and effort into them, and when they are finally done, you'll have something you can truly be proud of.
One of the most important things to a map is brushwork. New mappers often do not understand how to use the vertex minipulation tool, or the clip tool. These are essential to learn. Without them, your map will end up looking extremely blocky. Even iceworld, one of the most basic maps, has parts that were created using vertex minip. and clipping. Interesting brushwork makes maps so much better looking. Read about vertex minip here: http://countermap.counter-strike.net/Tutorials/tutorial.php?id=11 . What looks better? A huge square doorway, or an elaborate arch? Another way to spice up your brushwork is the use of angles. Putting your some walls at 45 degree angles can look much better than just the repetitive 90 degree corners again and again. Here is an example and a tutorial of the 45 degree trick: http://countermap.counter-strike.net/Tutorials/tutorial.php?id=51. Also, there are preset shapes you can make instead of just cubes. Try setting the block tool to create cylinders, arches, spikes, and wedges. Experiment a little, and things will turn out nicely.
Textures can make or break a map. Please, do not limit yourself to the low res half-life textures... they are horribly blurred, overused, and overall unappealing. There are hundreds of custom wads out there that will make your map look 200% better. Another alternative, for the more artistically inclined, is creating your own textures. I highly recommend practicing with Photoshop and how to make wads with Wally. If you know how to make your own textures, than whenever you need some extra detail on something, you can do it yourself. If your in need of a certain texture, you can just wip on up on the spot. Its so much easier, and gives you much more flexibility. Now also relevant to texture choice, is texture alignment. Properly aligning your textures using the texture alignment panel can make your map look absolutely excelent. If not, you will have a poor looking map with seams and, well, obviously, unaligned textures. Remember to scale your textures properly as well. Another thing often overlooked is the sky map! There are hundreds of custom skys out there, there is no need to use the crappy desert skies that come with the game. Choose a sky that is appropriate for your map.
Lighting is very import to Counter-strike maps, as it often sets the atmosphere, and provides cover and hiding places. Many new mappers often leave out lighting in their first map, causing it to be compiled in FULLBRIGHT. That term means that, because you have no lights (or possibly an error in your compile causing Rad to not complete), every single texture in your map gives off white light at the highest intesity. This is hazardous as the light can sometimes sizzle people retinas, and the same thing applies for bright colored lights, which we will get into soon. FULLBRIGHT also results in the lack of shadows, which looks odd in itself. Shadows add realism and hiding places, you need good looking shadows. Now for lighting, you have 2 choices: point based lighting, and textured lighting. Textured lighting is much much cleaner and better-looking, and is easier when you have alot of lights. Check it out here: http://countermap.counter-strike.net/Tutorials/tutorial.php?id=48 . Still, many times point based lighting is still appropriate, expecially for lighting effects. Read more about them here: http://countermap.counter-strike.net/Tutorials/tutorial.php?id=52 . Finally, onto the colored lights. Some newbies go overboard with this theme, so I'm warning you: colored lights are usually ugly and hurt the eyes, expecially when you have hundreds of multicolored bright lights everywhere. One last thing, entirely dark maps are usually not very fun, as only the CT's can buy nightvision, and there is absolutely NO WAY to equip it using entities. Its good to have a bit of a variety of light and dark areas in your map.
Many many first maps are fy_ or dm_ in style, because new mappers are experimenting and still learning, and are probably afraid to tackle a really large map. What we end up with is a map that is pretty small, and is simmetrical. Why do newbies resort to simmetry? Well, its easy, you only have to build half the map, and then its always fair for both teams, not to mention ridiculously easy for players to learn. However, simmectrical maps are also boring after a round or two. Good maps have a nice large layout to them, with a couple of paths to bombsites or hostages. For de_ maps, the best layout is decidedly the figure 8 layout, and you should probably look into it. For cs_ maps, the layout is a bit varied, and there is no real definative layout. As_ and es_ maps usually start out with many paths, that slowly wind down to one or two leading to the escape point. Its good to try and imagion where the fighting and chokes points will be, so you can accomedate those areas as neccissary.
Good maps have detail, simple as that. Without details, maps are usually empty and boring. So, when your creating your office building or whatnot next time, add a desk. On the desk, add a lamp. Put a couch in the room, put paintings on the walls, add some filing cabinets, some chairs, cabinets, a fishtank, a box of tissues, etc etc. Detail makes maps more interesting, realistic, and gives them a better atmosphere. The lack of detail makes maps bland, empty and boring. Models and textures (transparent textures too) can really help to add detail without adding lots of polies. We've only talked about brush detail as of now, but you should know there is other ways to add detail. Ambient sounds and sound effects really add to the atmosphere of the map, and make it less dull and boring, and feel more alive. Look at aztec: where would it be without the lightning strikes and the chirping crickets? Read this tutorial for more info on sounds: http://countermap.counter-strike.net/Tutorials/tutorial.php?id=17 . Also, I count lighting and shadows as detail aswell, don't leave them out.
It is important for your map to vary from area to area. What I mean is that each room doesn't look exactly the same, there is a landmark to each area. This can be done through decals, brushwork, or textures, just remember to stay inside your theme, so your map matches so to speak. Another important ideal is elevation. Variation in height can provide tatical importance and cover. Look at de-dust2, which is one of the most profound and best examples of height variation. Also, cover ofcourse is important. Please do not limit yourself to crates, there are a thousand and one other ways to do it. Rocks, building, debris, walls, furniture, cars, trucks, planes, hills, etc etc etc. Read this tutorial for more help: http://countermap.counter-strike.net/Tutorials/tutorial.php?id=35 . Entity work can also make a map more fun, but remember not to add any "suprises." Typically, players do not like a map where there is a button and it kills everyone... those kind of inescapable traps are no fun. R_speeds are also VERY important. Be sure your maps r_speeds do not go above 800, atleast not in an area where there will be lots of combat. There are ways to reduce r_speeds, look here: http://countermap.counter-strike.net/Tutorials/tutorial.php?id=19 . Hint brushes can help, read about them here: http://countermap.counter-strike.net/Tutorials/tutorial.php?id=2 and here: http://countermap.counter-strike.net/Tutorials/tutorial.php?id=54 . Another note, somewhat related to r_speeds, is the use of models in a map. Models can add detail to maps without adding polies, and now, using Hammer 3.5, we can even see models in hammer making it easier to clip and place them. YAY!