Game Design Tutorials for Unity3D
LuclinMCWB gives a variety of practical tutorials in game design, especially in Unity3D environment. The tutorials are published on YouTube under minecraftwb username.
There is a tutorial in Basics of Unity3D and Terrain Design which is very handy for beginners in Unity3D:
Other tutorials demonstrate how to import objects and assets into Unity3D and how to further work with them:
You can also find some more tutorials which might be particularly useful for your game design work: