Regarding set up of VU Led

i bought a vu led 40". i want to know what will the best configurgation of picture means what value should be selected in contrast colour sharpness etc so that clarifty of screen will be good. as of now hd channels are looking very good in quality but non hd channels are not.

the boy who came for installation was not having so much knowledge of the product and he has not given me demo of the product thats why i am asking. is there any site where i can check all the information regarding this.