How to prevent rashes in new born baby?

Too broad. The question is very broad. Could you ask it again and be a little more specific. What kind of rash are you trying to prevent? Diaper, dry skin, illness?
Sensitive skin. Newborns have very sensitive skin and many rashes are common, but not harmful. Clean her skin with clear water, using a mild baby soap and rinsing well. Do not use products with a lot of chemicals or perfumes. Avoid baby lotions and powder (talc). Keep her skin cool and dry- don't overdress and don't allow her to overheat.