The Tips in detail

 "Use noise for realism."

In most cases textures, lights, atm-FX and objects are not plain or smooth or regular or even.

Noise is the key to realism in these cases. You can add noise to almost everything. Just look around in the modifiers.

Cases of "must use" especially occure during animations. I often see cameras moving around as if they were mounted on some kind of floating robotic device.

Have you ever seen a really plain floor? If you look at how cameras behave in movies you will for sure notice, that they almost always have some swift and smooth curved path. Not only concerning x and y axis but the z axis aswell. Keep in mind that every "room" has three dimensions: width, depth and height. Many amateurs move their cameras around on x and y, but the z mostly stays the same.

To shake up yor camera-path you might want to add a positional noise to get a slightly irregular path by shaking the z position.

If you are using atm-FX using noise is almost always a must. I don't know about a fog that is perfectly constant by any means and smoke is everything else but constant, even when you are standing inside and look out of it. Not using noise here directly leads towards unrealistic images.

Lights are suffering from various influences such as atmosphere and in many cases the source is not constant (eg. fire, sunlight). You will have to use a noise of several projected colors to get realistic natural light.

Concerning the surfaces of any given object you will notice that thier real-life counterparts might feel smooth, but they are not looking smooth from every perspective. To get this done you will need a noise-mapping inside your bump-map or a noise on the mesh. The first one can be achieved via the material-editor, the second - for example - via a displacement modifier on the object itself. Both have pros and cons. The main pro for the material variant is that it can be modified quite easy to fit your needs. The con is, that you don't really add bumps since the object's mesh stays smooth. The pro for the mesh variant is, that it does result in a much more realistic object but at the cost of the need to increase the face-count.