The ideal is to not touch them at all. Picking them up with a container of some sort is preferable. The oils in our hands, residue from soaps/creams, etc are a potential danger for their permeable skin, not to mention the fact that our body temperature is lethal to them so prolonged exposure to body heat can result in death (not usually a problem if you are dipping your hands in cold water, but something to definitely consider).
Latex gloves should be avoided and powdered ones are a definite NO since they cause mortality.
Like Dawn has said, if you must handle an amphibian you need to make sure your hands are thoroughly rinsed, wet and that you minimize the surface and the time of contact. But really, no contact is definitely preferable.