A newborn's nails grow quickly. To trim baby's nails, use baby nail clippers, nail scissors, or a file. First, give baby a bath to soften his nails (and hopefully make him sleepy). Then lay him down or sit him in your lap.
Press each finger pad away from the nail so the nail sticks out. Snip just the white part, leaving a bit so you don't accidentally cut too low. Expect to do a trim two to four times a month. You should only have to cut baby's toenails once every few months.