Which better to make the bokeh effect?

AF 50mm/f1.8D or 70-300mm VR or what is the best lense for nikon d5100 that i can make bokeh effect for all the body in the pic and also for the upper body? I need help to know how to make the bokeh effect in nights etc

Use the 50mm at f1.8 to get bokeh. Make sure the background is a long way away from the person.

It is a myth that you need a fast lens for limited focus (what you call bokeh), especially on a lens with a shorter focal length. I have achieved equal or better results with a 200mm lens @ f/5.6 vs.a 50mm @ f/1.8.

The single most significant characteristic to produce limited focus is the focal length. Therefore, if you can get your subject framed at 300mm, it will likely provide a better result than a 50mm f/1.8.

Here is a webpage showing different examples of focal lengths and apertures. It proves that the focal length is more important than aperture, and I even was able to get some degree of the effect with a compact camera.

http://www.althephoto.com/concepts/selectivefocus.php

It is more technique than equipment.