I am trying to render a single image of a normal A3 image, however, it took me a very long time to process the rendering. Is there any specific settings for the render so that I could get a quick good quality image?

Speed vs. Quality.

It depends upon how low/noisy you are willing to accept as your final output.

In the Mantra node, under the Rendering TAB and under the Sampling TAB I generally set my SamplesX,Y to 2 and set the Min Ray Sample to 2 as well. I also increase the Tile Size from 16 to 48. This gives me a little speed up from the default settings of the Mantra node.

Try using only one light. If you have multiple lights solo each one and determine if any one light might be slowing down the render more than another.

If you have glass and or reflection materials in the scene set their bounce values as low as possible, generally 3 is a safe low number, Mantra defaults to 10.

If you still have Ray Variance Antialiasing turned on go ahead and increase the Noise Level from 0.01 to 0.1. This is the chance a ray might need to sample again.

Maybe more info about scene, render?