EA has started its latest Developer Blog Series; this one by Jeremy Feasel and deals with designing multiplayer maps.
The goal throughout the development of RA3 was to create a multiplayer experience that would appeal to a wide audience. We've added quite a variety of map sizes, from small, "knife-fight" 1v1 maps that are the favorites of our fast-click, hardcore MP crowd; to sprawling forests with multiple lanes, elevations, and back-doors, for the thoughtful meta-map strategist. Great map design can add depth by expanding the core experience across a variety of scenarios.
We take a similar approach when considering other important map elements. Garrison distances from major choke points, ore nodes, and points of interest are carefully measured to allow for optimal coverage of that combat area and usage of the garrison/degarrison mini-game. Points of interest, such as oil derricks and other tech buildings, are placed in areas where early-game combat should occur. Expansion points are set up to allow for various levels of player choice: do you take the risky expansion close to your enemy, or the safe expansion that is off to the side and away from your main force?
This becomes especially complex with the naval focus of RA3. The relative power of a player's navy is strongly influenced by the amount of water and ocean-hosted ore nodes on the map. After a few test cases, however, you come up with a system for crafting the "relative aqueousness" of a map. (Ah, sweet aqueousness. I think I just made that word up.) In other words, specific combinations of ore node risk, combined with location, push a map's focus more toward water or land. Neutral structures can also be used to push a player off of their main island early, or force players to fight over a terrestrial area. The key is understanding how the widest range of people play, and that comes from observing a large variety of players and gameplay styles.
Be sure to to check out the rest of the blog here as well as some nifty new radars of multiplayer maps he's created.