Instructions
Focus on building single level maps until you have a firm grasp of map design. Multi-level maps are complicated and consideration must be made of competitive advantage and accessibility.
Try to add at least two entry points to every spot on the map. Areas with one entry point suffer from player camping, which is a form of ambushing.
Imagine how players will move about your map. Every map has a natural flow, and understanding the flow of your map helps prevent traffic jams and keeps players moving in the right direction.
Make it easy to find other players. Large maps should have very little visual clutter, while smaller maps can have larger buildings and more cover. Trying to find other players is the most frustrating part of any poorly designed map.
Time the various team paths to certain objectives in your map. Team objectives should be evenly spaced from starting points to ensure the map is fair.
Weigh the risk of certain paths with the advantage. For example, cutting across a piece of debris may be the fastest way for a potential player to pick up a rocket launcher, but he exposes himself by doing so. Good maps have at least a few risk vs. reward choices.
Invite a few friends over to playtest your maps. The best way to check your map quality is by gathering feedback from players.