My grandmother

[marc]

The less a person knows the louder he talks.

[James Rondon]

That's not always true, but it is true, often.

[Charles Sloan]

The less a person knows the louder he talks.

Would that be something like:

"It is better to remain silent and let and be considered a fool than to speak and remove all doubt."

[mikeyjc]

 
Throw a stone at a pack of dogs and the one that gets hit yelps.

[janine]

Run it up the flagpole and see who salutes?  Throw a lot of mud as the wall and see what sticks?