Ok well this is my guide to simple map design. Yes i did read this on the Treyarch wiki but thought i'd put it into my own words.

Right so first of all you want to have an idea, a vision. Now ask your self these three questions:
1. Should the centre of the map be open, so people can dash through it and probably get shot thus forcing play around the edge of it. Or, should it be a building where the play is most intense and the open out skirts provide moving space for the other players.

2. Should the spawn points be open, making them easier to capture and makes the speed of the game faster as you quickly swap ends, or should the spawn points be CQB (close quarter battle) thus making the last bit the hardest.

3. Wide, long or square.
  - A wide map: It's quicker to get from one end to t'other, perhaps just make the middle wide so that the more intense play is closer to the spawns and thus players can be stealthy and tactical about slipping around the big centre to the map.

  - A Long map: More common because players are forced to play against each other (can't slip around), here you want to make sure each side has equal opportunity when it comes to cover, getting high up and 'flanking'. You want to ensure there are more smaller routes so that in the close quarters you have the opportunity to outwit your opponent and run inside... then upstsirs and jump down behind them etc.

  - Square maps are not very common, usually you want a main middle bit and an outside part, where play is centred around one building or area and the bits around it are for flanking etc. Maps which do this well are WaW: Corrosion. Also maps like MW2 Wasteland are square and make players 'go in circles' where the hot spots are the corners. A central tunnel provides opportunities for flanking etc. Square maps need careful consideration but can be very fun!!!

When you know what you want it is time to design your map... but i'll add that later

***OK***
 Now lets think about the map.

3 MAIN ROUTES... Any freaking CoD map, 3 sodding main freaking routes!!! Get that in your head.

I would start with the middle, that vision you have that would make a great map. Draw that first! Then work out.

Think about + design
1. The north  + south enterances to this middle bit, then the two routes around it (assuming it is infact in the middle), now join the middle up to these two flanking routes so you have a square with a cross in it kind of shape:
___
|+|
----

Now you have your middle, now design the north and south spawn points. Remember, did you want them to be open spaced or confined? Now make some extreme flanking routes... like right around the edge on Cliffside. These should be a quick + rewarding but risky option.


Think about where to place the A and B search and destroy objectives. I always design a map thinking about search and destroy, these objectives should be in places where game play meets and where the best fighting is. Now you can go into more detail, planning out rooms and buildings to provide routes around the objectives to avoid hot-spot and attack it.
 - Remember the objectives should be closer to the Defenders spawn, but still make it fair!

By now your map should be fairly detailed.

Now look for long gaps, where people might be too exposed, where a noob with a GL or MG or sniper could camp... or simply spaces that need filling. Sometimes the most effective thing to do is dump a destroyed half-track to provide some cover!

More to come.

I'd never actually seen this on the Treyarch wiki... this is good info!