Found an interesting article a few days ago asking various professional game designers a simple question: What’s one thing you wish you had known before starting as a game designer?
You can see the full article here: http://makeboardgame.com/20-board-game-makers-chime-in-what-i-wish-id-known-before-starting-my-board-game/
And my two favorite quotes are duplicated below:
This strikes a chord with me from my Dinosaur Cowboys work, where I was tempted to add more mechanics, equipment, skills, etc. to satisfy the growing understanding and playtime of my friends. When realistically the game is fairly well tuned for new and experienced players. Just need to take a step back sometimes and really consider why you’re adding a rule/new system, and if it fits into your original vision.
Which leads nicely into the next quote…
Very, very true and important to keep a clear picture of what you are trying to achieve with your game. In fact even having a well defined big picture view in the first place helps a ton. Because then when you’re going to add a new mechanic you can ask yourself: does this fit my game concept? Basically test yourself each time you want to change or add something.
From my experience my Life of a Dinosaur Cowboy RPG had the problem of a lot of cool mechanics that led to a not very cool or fun game. Very easy to lose sight of the forest through the trees.