Here is a few things to take into consideration while coming up with a design for a game.
The design should always have the player in mind when designing a game. Being able to objectionally see how a player may play the game will lead to a better gameplay experience for the player.
When and where possible and appropriate always and for every input provide feedback to the player. Even if it's an “I don't understand” response.
The player always needs a sense of direction. At any given point the player should have an immediate goal, a mid range goal, and an overall goal. Without this the player may loose interest and stop playing the game.
The player should always be entertained. The moment the player finds himself standing there waiting for something to happen, he'll potentially walk away from the game. This may not be a bad thing if your game is long and needs places for the player to stop and take a break. But the game should compensate for this and have a draw that brings the player back to the game. On the other hand if the game is reasonably short then we don't want them to become bored because they'll never come back. One last point, it's import not to give the player repetative tasks just to keep them occupied. Also, any cut scenes need to have the ability to bypass them.
Another point to be considered is the player's save points. Always strive to allow the player to save when they want to. Also allow them to name the save anything they want. Taking this into account will allow the player to pause the game whenever he wants as well.
The player should feel like he is actually in the game. Things that break this vivid “dream” need to be smoothed out so they don't jar him from this fantasy.