First-Person Grid Based Movement

I'm struggling with something and was hoping someone might have a few pointers for me.

I'm try to create first-person movement in a style similar to the old-school RPGs like Eye Of The Beholder.

I basically want to place four movement buttons on screen over my 3D environment. When the user presses the forward button, the player object should move forward x points. When the user presses the left button, the player should rotate 90 degrees left, etc, etc.

Does anyone have any examples...

First-Person Grid Based Movement