Five Skills

There are five major components that make up the skill set required to be a complete game designer (although no one person excels at them all). These are System Design, Content Design, User Experience Design, Communication Skills, and General Knowledge. The following is an outline of these components, which if fleshed out would make a great book on game design. If you decide to use this outline as an inspiration for such a book, make sure you send me a free copy...
 
SYSTEM DESIGN
System design is the core nuts-and-bolts skill of the game designer. This is the engineering side of game design: how does the game actually work?
  • Core Game Mechanics: Designing the basic rules by which any game works, regardless of medium.
  • Conflict Systems: Designing systems of rules for dealing with direct conflict, usually simulating real combat.
  • Economic Systems: Designing systems of rules for dealing with trading, growth, investment, logistics, etc.
  • Social Systems: Designing systems of rules for dealing with emotional and social connections between players and/or characters.
  • Algorithm Design: Designing the mathematical algorithms that underlie the all the systems listed above.
  • System Analysis: Determining how an established or proposed system works or will work, and where it will break down.
  • System Balancing: Making a system have multiple "correct" strategies, none of which is obviously superior to the others. Also includes getting the difficulty curve right.
  • System Tuning: Fine-tuning a system so that it works cleanly, efficiently, and elegantly, with only the minimal set of rules needed. Also includes proper pacing, when relevant for a given system.
  • System Integration: Making multiple systems work together as a coherent whole in a single game.
  • System Synthesis: Taking individual mechanics and algorithms from multiple sources and synthesizing them into a new system.
  • Meta System Design: Designing systems that tie other systems together into a overarching meta-system.
CONTENT DESIGN
Content design is just as important as system design, but it is the artistic side of game design. Most game designers can be categorized as either system designers or content designers, although some can do both.
  • World Design: Designing the background, geography, history, social order, cosmology, science, etc. of the world in which a game takes place.
  • Level Design: Designing specific areas in which game play actually occurs, making them interesting, fun, and properly balanced.
  • Puzzle Design: Designing individual obstacles or challenges to overcome in a particular level, making them interesting, fun, and properly balanced.
  • Resource Design: Designing items (broadly defined) used by a player or other character, making them interesting, fun, and properly balanced.
  • Character Design: Designing the background, personality, motivations, abilities, weaknesses, etc. of characters in a game.
  • Dialog Creation: Writing the specific dialog used by any character in the game, making it interesting, snappy, and memorable.
  • Story Creation: Writing the plot of the overall game and any sub-plots, making it interesting, well-paced, and memorable.
USER EXPERIENCE DESIGN
System design and content design will get you a game, but user experience design will make it a game people actually want to play.
  • Interface Design: Designing the player's entire interaction with the physical components of the game (including user input, menus, HUD, etc. for computer games).
  • Playtest Design: Designing playtest sessions for a game that will actually produce actionable information about any aspect of the game.
  • Playtest Analysis: Taking data and observations from a playtest session and figuring out what to pay attention and respond to versus what to ignore and discard.
  • Concept Translation: Taking an abstract concept of what a player should experience and translating that into an actual step-by-step user experience.
  • Player Empathy: Understanding how a game works from the point of view of a player, whether that player is an expert or a complete novice. Includes understanding player motivations, prejudices, limitations, etc.
  • Player Research: Researching which types of players are interested in which types of games, including how to present new game designs in a way that will appeal to current players.
  • Game Research: Researching current and past games to understand what has worked in the past and what your current competition is doing.
  • Targeted Design: Designing a game for a particular narrow set of users or a particular cultural market. Also includes designing a game for a particular product, service, or peripheral.
COMMUNICATION SKILLS
Someone can be the best designer in the world, but unless he is also an artist, musician, programmer, etc. his designs are useless if they cannot be effectively communicated to the people who actually build the game.
  • Documentation: Using written communication to convey the actual design of the game to other members of the team, in a way that each discipline (art, programming, marketing, etc.) can use effectively.
  • Presentation Skills: Using verbal and visual communication to effectively convey broad overviews of a design to other members of the team, especially to management and executives.
  • Brainstorming: Organizing and leading brainstorming sessions to solve design problems. Includes choosing the right people for each session, synthesizing the results of the session, and only integrating the right ideas into the actual design.
  • Prototyping: Creating paper prototypes or directing the creation of computer prototypes to test various designs and show, rather than tell, how a particular game will work.
  • Taking Criticism: Soliciting and taking criticism of your designs in an effective and polite manner, encouraging very direct feedback, digging deeper into disagreements to find out where the conflict really lies, being able to reject inappropriate criticism politely, etc.
  • Giving Criticism: Criticizing other game designs effectively and politely, in a manner that allows the other designer to actual make their design better.
  • Delegation: Delegating design tasks to other designers as appropriate, in a manner that gives them clear expectations of the results needed, but also gives them the power to make decisions without being micromanaged.
  • Cross-Discipline Communication: Communicating with other disciplines frequently so that they understand what is important to you and what isn't so they put the right amount of effort into solving the right problems. Also includes adjusting your designs in response to feedback from other disciplines when appropriate.
  • Inspiration: Getting your entire team to buy in to the vision for your game and become dedicated to making it as good as possible.
GENERAL KNOWLEDGE
Good game designs cannot be created in a vacuum. A designer must have a broad knowledge of many different topics in many different fields (note that breadth is generally more important than depth for a designer).
  • Cross-Discipline Knowledge: Having at least a basic understanding of art, music, programming, marketing, etc. will make a designer much better at communicating with the rest of his team.
  • Hard Science: Basic knowledge of physics, chemistry, biology, astronomy, kinesiology, etc.
  • Social Science: Basic knowledge of psychology, economics, archaeology, anthropology, etc.
  • Liberal Arts: Basic knowledge of history, languages, writing, philosophy, architecture, etc.
  • Cultural Knowledge: Basic knowledge of different customs, sports, fashions, religions, etc.
  • Research Skills: The ability to get a basic working knowledge of any topic very quickly.
BONUS MATERIAL
As a bonus for reading the whole thing, here's my take on how the game design discipline should be organized, based on experience and overall role.
  • Junior Designer: A designer just starting out with no professional experience. Assists more experienced designers and is given lots of direction and guidance.
  • Game Designer: A designer with at least a few years of professional experience. Capable of independently designing smaller games, or parts of larger games.
  • Senior Designer: A designer with five to ten years of professional experience. Capable of independently designing a line of smaller games or an entire larger game.
  • Design Architect: A designer with more than ten years of professional experience. Capable of driving the design of dozens of smaller games or multiple larger games.
  • Design Visionary: An elite designer of multiple hit titles capable of driving the design direction of an entire studio and influencing the direction of the game industry itself.
Instead of becoming a senior designer, a game designer could take the management track instead, which would work as follows:
  • Lead Designer: A designer who manages other designers (of any skill level). This position and above is based on management ability, not on design ability.
  • Design Manager: A designer who manages lead designers. This is usually the highest level manager in the design discipline except at large studios.
  • Creative Director: A designer who manages design managers and is responsible for overseeing art and audio as well. This person might come from the art or audio discipline instead, assuming they have decent game design skills as well.