One night, when Samuel was an older boy (probably around 12 or so), he was sleeping in the Sanctum Sanctorum when he heard a voice calling his name. He assumed it was Eli calling, since Eli was old, blind and in bed. So he went into Eli’s room, but Eli was all, I didn’t call you. Go back to bed.
So Samuel went back to bed, but no sooner had his eyes closed then the voice called his name again. Again he went to Eli and received the same answer. So he laid back down, and the voice called a third time. This time when he went to Eli, Eli decided it must be God calling, so he told Samuel that if he heard the voice again to answer, Speak Lord, for your servant hears.
Then Samuel went back to his pallet and when the voice called him the fourth time, he answered, Speak Lord, for your servant hears.
So God spoke, and spent the night telling this boy about how God was going to utterly destroy Eli, the man who raised him, for permitting his sons’ sinfulness, and the sons for being dicks. After God left Samuel alone, the boy spent the rest of the night fretting about Eli’s fate and whether or not he should tell the old man what God said.
The next morning, Eli of course asked what God had told Samuel, but the boy just hemmed and hawed and equivocated until Eli scolded him and told him to tell what God had said upon pain of Eli’s curse. So Samuel told him that God had said It was going to destroy Eli and his family. Eli sighed and said, Let God’s will be done.
From then on Samuel’s chats with God became more frequent and he began prophesying regularly until his fame and his name was known from Dan to Beersheba.