With one hand on him. Never leave a baby unattended, even for a second, in a bath. For basics, here is a good summary from the aap http://www.Healthychildren.Org/english/ages-stages/baby/bathing-skin-care/pages/bathing-your-newborn.Aspx.
Gentle, Infrequently. After the cord falls off, prepare a lukewarm bath, i like use of an organic bar soap from the middle of nowhere in montana that allows one hand to wash (hair included) and one hand to hold, remember babies skin will be healthiest with infrequent bathing, every other day, even every third day. Never leave baby unattended even with the fanciest contraption in the bath. Oh, and enjoy!