General Rendering Values

I was wondering if there is a general guideline for exterior renderings (architectural buildings) using iRender NXT through sketchup. In particular: values concerning window transparency values, reflection values, lighting values (both day time and night shots). I am pretty new to this program and we are starting to use the renderings for client presentations, so I would like these to look as professional as possible.

Are there any general guidelines out there to input specific values (without spinning my wheels of trial and error)?

Thanks,

Mike