1 Samuel 1-6: Samuel, A Willing Heart

The boy Samuel ministered before the LORD under Eli. In those days the word of the LORD was rare; there were not many visions.
One night Eli, whose eyes were becoming so weak that he could barely see, was lying down in his usual place. The lamp of God had not yet gone out, and Samuel was lying down in the temple of the LORD, where the ark of God was. Then the LORD called Samuel. Samuel answered, “Here I am.” And he ran to Eli and said, “Here I am; you called me.” But Eli said, “I did not call; go back and lie down.” So he went and lay down.
Again the LORD called, “Samuel!” And Samuel got up and went to Eli and said, “Here I am; you called me.” “My son,” Eli said, “I did not call; go back and lie down.”
Now Samuel did not yet know the LORD: The word of the LORD had not yet been revealed to him. - 1 Samuel 3:1-7 NIV

"In those days, the word of the Lord was rare."  That phrase is reminiscent of the one repeated over and over again in Judges "In those days, there was no king, the people did as they pleased."  Of course, there is a correlation between the people doing as they pleased and not hearing from the Lord.    God only speaks to willing hearts, to those who will listen, and not just listen, but obey.

Most people really don't want to hear the word of the Lord.  They don't want to hear what God requires of them. They don't want for his word to be revealed.  Samuel was one of the rare ones who would listen when spoken to.  The slightest whisper from the Lord was enough for him to perk up his ears, ready to do whatever was asked of him.  At first, he thought it was Eli calling him.  He was eager and willing to serve the voice that called him.  When Eli tells him that it is the voice of God that is calling him, he is not afraid.  "Speak, Lord", he says, "for your servant is listening".  Finally the Lord has found someone willing to listen, someone who is concerned with the desires of God more than with his own well being; someone who is not afraid of the words he will hear, but who is ready for whatever action is required, who is willing to serve regardless.

Like Samuel, if we want to hear the voice of God, we have to be willing to act on what we hear.  If we don't hear from God, it is because he knows the willingness of our hearts.