When you pay attention and consider something's importance, you heed it. The word 'heed' can also mean being careful not to do something, like heeding a warning to stay away from danger. Heed is often used in phrases with the verb "give", as in "Give heed to my words" which means pay close attention.
Heed usually implies taking action because of what you've noticed or been told. If someone gives you advice, try to heed it and act on it. A teacher might ask students to heed their warnings about a tricky subject. If there's construction going on near your home, you should probably heed the warning signs and stay away for safety reasons.
Careful attention.
To guard, protect.
