wet behind the ears

(idiomatic) Inexperienced; not seasoned; new; just beginning; immature, especially in judgment.

Example: 1903, "The Boy Whose Parents Wanted Him to Be Useful," Chicago Tribune, 2 Aug., p. B2 (retrieved 5 Oct 2010):
  [They would put] their hands behind their ears and pat the top of their heads to taunt me with the fact that I was still wet behind the ears and soft on top of the head.
1950, Roger Appleton, "Police to End Teen-Age Gambling: Strike at Pool Hall Hangouts," Ottawa Citizen (Canada), 13 Jan., p. 18 (retrieved 5 Oct 2010):
  Every week day, pool rooms are filled with scores of boys still "wet behind the ears" who have no business anywhere but in the classroom.
1991, Dick Thompson, "The Man with the Plan," Time, 15 July:
  Now, here was the freshly minted FDA commissioner, still wet behind the ears at 39.
2004, Jarrett Bell, "Bengals' Kitna 'classy' about losing job to Palmer," USA Today, 8 Sept. (retrieved 5 Oct 2010):
  "These young whippersnappers are still wet behind the ears."