You mean, volumetric lights? To really create a visible volumetric light, your scene has to be dark. Or at least has to have sun turned off. On the pic is a simple spherical light with strength of 125, set to squared and Infinite light. The same result can be achieved by using the default strength and linear. Or do you possibly want something like on my _Death Metal_? (My gallery.) I did play with ranges on that one. but the most important thing is to turn off the sunlight.

-- erlik