The answers to the following clues will have something in common.

1. Garden of Eden paradox
2. Influence peddler's motto
3. Look or leer
4. Familiar with the way things work
5. It put a man on the moon.
6. Classic gangster film line
7. Arlington honoree
8. Familiar trouble vs New trouble
9. Having confidential information
10. Self-styled genius
11. Why girls go to college, according to the jump rope rhyme

Answers:

1. Tree of Knowledge
2. It's who you know
3. Knowing glance
4. Knows the ropes
5. American know-how
6. "He knows too much."
7. Unknown soldier
8. The devil you know
9. In the know
10. Know-it-all
11. To get more knowledge