Most games have a tight design around what the beginning of the game should feel like, the middle, and the end making sure to keep a good pace but also changing in intensity as the game plays out.
describe how each state of the game will play out, and what some of the player's goals and objectives will be during these times.
Heres a good article on the topic to get started http://game-wisdom.com/critical/states-of-game-game-design
Use these resources we have and start a forum where other members of the team can discuss this. Once we have everything we need to create a document illustrating the topics and things we discuss so that others can refer back to it when designing certain elements of the game
