Idly throwing a pebble into a lake or a deep hole in the ground, in a place where monsters lurk, and when you know the company is trying to pass by as quietly as possible, unnoticed by anyone :).
Not paying attention to the advice of your friends including new friends you make on your travels -- for instance when they tell you to keep good speed, then just possibly that means it's not the best time to have a long midday nap on the barrow downs.
Telling anyone you meet what your secret mission is (unless you are Sam when it might be that blurting it out by mistake is just the right thing to do at that moment)