- Judge from your experience
Why did you make your previous game? One possible answer is to use the knowledge and experience that I got developing it for my future projects.
Analytics will help you spot and never make the same mistakes again. Building it into your every project is a must, and the more of it, the better since it's a way to know the user's behaviour in the game inside out. For example, in one of my kids' projects I wanted to add a narrative element by making a beautiful cinematic intro, in which the player is told about the plot of the game.