"Use your head for more than a hat rack"
Straight and to the point this means to stop being stupid.

"Look beyond your nose"
As an adult its self explanatory, the operative phrase here being "as an adult".

"Put your mind in motion before you throw your tongue in gear"
Needless to say this was said in a futile attempt to keep me from opening my mouth and inserting my foot.

"You know what happened to the banana when he left the bunch, he got skinned"
Short and simple don't stray to far, you will regret it.