One simple tip that can enhance your renderings is taking advantage of the ambient occlusion provided in vray. Ambient occlusion wasn't available back when I started using Vray. Ambient occlusion is basically a simplified way of using vray dirt in the scene.
The first scene is rendered without ambient occlusion. The walls are bright and joints and the corners of the ceiling isn't that well defined. There are also a lot of over blown highlights in the scene.
If you turn on the Ambient occlusion and use the default settings, you will notice the scene has become a bit darker and noisier. The corners and joints are a bit defined but at the expense of darkening the scene and adding more noise.
In order to restore the brightness of the scene you need reduce the radius of the ambient occlusion. By reducing the radius to 3 meters the walls and ceiling has brighten up but the noise in the scene is still a bit distracting.
There are different ways to reduce the noise in this scene. The most direct way to reduce the noise is to adjust the Subdivs in Ambient Occlusion. Increasing the Subdivs to 16 dramatically improves the noise in the scene and enhances the details on the corners and joints.
Turning Vray Ambient Occlusion enhances the details in the corner and joints. Depending on the complexity of your scene, render time may increase a bit. Since this scene only has a few objects in it, activating Vray Ambient Occlusion hasn't drastically increase the render time. Although there might be a slight increase in render time in scenes with multiple objects, the results on the final render using ambient occlusion is definitely worth it.