Level Design

This may sound a bit "broad" However, I'm currently creating a scene in Unity. I've imported some models from Blender into the scene (None of which are textured as of yet). But I'm wondering how I can make it look more "realistic", instead of just block colours and textures that just look like a photo slapped onto the face of the model. Obviously lighting and shadows play a part, and more complex model designs etc. Anyone got any tips or tutorials to help me?
Thanks

 

Normal/height maps have a lot to do with making it literally pop out (look less flat/pasted on). No idea how you bake 'em in Blender though.

Another thing to do is to grunge it up. Yes, cover it in filth. Not all buildings are squeaky clean!

 

Thats exactly what I'm trying to do. I'm attempting to make a call of duty type game, so smashed up, stripped down, beat up buildings and rooms is what I'm after, or "Codenizing" as I call it.