Speaking for the user. But not being the user, it’s a big work of empathy. This distinction is important because most people using your product do not have the same expertise. You have to be a true guardian for their experience.
It’s all about visual communication. Creating digital wireframes, mockups, or interactive prototypes are the only way to reach the experience. Also there is beauty when something works and it works intuitively.
Always mastering the latest creative tools is the best way to craft the most efficient way. Currently my workflow is Sketch for UI, Blender for 3D, Unity as a game engine, G-Suite for sharing and of course my pencil and my communication skills.