Eli was the man of God responsible to teach Samuel about God and how to listen to Him and judge with knowledge and wisdom. However, Eli wasn't really on the ball. His sons were appointed priests over Israel but they were sons of Belial-they worship and pledged their lives to a false god. They used the office of priest to make themselves fat with the offerings of the people. They despised the Lord and took what was not rightfully theirs and Eli didn't do anything about it. Eli was even told by a Man of God that his household would be cut off from Israel because of this transgression. (I Sam 2:12-17, 22ff) So, in the absence of viable spiritual leader and teacher God took care of Samuel.

I Samuel 2
:26 And the child Samuel grew on,
    and was in favour both with the LORD,
    and also with men.

Because of Eli's lukewarm stand with God Eli wasn't looking to God and God wasn't talking to him.

I Samuel 3
:1 And the child Samuel ministered unto the LORD before Eli.
    And the word of the LORD was precious [rare] in those days;
        there was no open vision. [there was no revelation-Eli wasn't listening]
:2 And it came to pass at that time,
        when Eli was laid down in his place,
        and his eyes began to wax dim,
    that he could not see;
:3 And ere the lamp of God went out in the temple of the LORD,
        where the ark of God was,
    and Samuel was laid down to sleep;

God had instructed Moses in Exodus 27:20 to keep a lamp burning in the tabernacle always. This signifies the presence of the light of God. Eli let it go out. If Eli is not listening to God and taking heed to his commandments what is he really teaching Samuel? Well, God has plans for Samuel so He is going to have to teach him. One day when Samuel had laid down to sleep:

:4 That the LORD called Samuel: and he answered,
        Here am I.
:5 And he ran unto Eli, and said,
        Here am I; for thou calledst me.
    And he said,
        I called not;
        lie down again.
    And he went and lay down.
:6 And the LORD called yet again,
        Samuel.
    And Samuel arose and went to Eli, and said,
        Here am I; for thou didst call me.
    And he answered,
        I called not, my son;
        lie down again.
:7 Now Samuel did not yet know the LORD,
    neither was the word of the LORD yet revealed unto him.

Samuel had not been taught how to receive revelation from God-how to listen, how to recognize revelation.

:8 And the LORD called Samuel again the third time.
    And he arose and went to Eli, and said,
        Here am I; for thou didst call me.
    And Eli perceived that the LORD had called the child.
:9 Therefore Eli said unto Samuel,
        Go, lie down:
        and it shall be,
            if he call thee,
        that thou shalt say,
            Speak, LORD;
            for thy servant heareth.
    So Samuel went and lay down in his place.
:10 And the LORDcame, and stood,
    and called as at other times,
        Samuel,
        Samuel.
    Then Samuel answered,
        Speak; for thy servant heareth.

Put yourself in Samuel's sandals. I know many of us would fall over faint if God called our names audibly. Yet how is God going to talk to us? He has sent His Word, that is the primary revelation. Yet there are instances when we are in need of further information. This is where word of knowledge, word of wisdom and discerning of spirits come in to play. God communicates to us via our five senses-this is how we obtain information. It is also God in Christ in us-He is all in all. He is present in every part of our being. It is Christ behind our eyes. It is Christ behind our ears. It is Christ behind our hands, in everything-all in all.

God will communicate with us in ways that we understand Him. When we look at instances of people recieveing revelation from God they didn't stop and say, "Is that really you God? You know, I don't really understand what you mean." They knew full well what God meant. They didn't always obey and sometimes discussed the revelation but they always understood. God has not changed. With God's seed-the comforter, Christ in us, the gift of the holy spirit-God has given us the ability to hear, see, smell taste and touch His revelation and inspiration. God teaches His spirit which is in us which is now our spirit and our spirit teaches our mind. That is how God communicates with us. It is available to hear God, smell foul spirits, see revelation, feel danger and taste words. These are merely examples of how God can talk to us. The Old Testament has many examples and is full of knowledge about walking in the spirit and listening to Him.

Talking to God is not a one way conversation. We don't receive revelation from Him because we do not believe to. He is not in the neon signs, He is in the still small voice. If we are in turmoil we are not peaceful and listening to Him. "Be careful [anxious] for nothing, but in every thing by prayer and supplication with thanksgiving let your requests be made known unto God." (Philippians 4:6)

:11 And the LORD said to Samuel,
        Behold, I will do a thing in Israel,
        at which both the ears of every one that heareth it shall tingle.
:12   In that day I will perform against Eli
        all things which I have spoken concerning his house: when I begin,
        I will also make an end.
:13   For I have told him that I will judge his house for ever
            for the iniquity which he knoweth;
        because his sons made themselves vile,
        and he restrained them not.
:14   And therefore I have sworn unto the house of Eli,
        that the iniquity of Eli's house
        shall not be purged with sacrifice nor offering for ever.

Because of Eli's transgressions and his sons gross disobedience his household is unredeemable. It was the choice of Eli, God had told him previously and Eli knew the written word and chose not to obey.

Samuel was very reluctant to tell Eli what God had told him but Eli persisted and Samuel told him every everything and hid nothing from him. Eli acquiesced, he knew he had done wrong.

:18 And Samuel told him every whit,
    and hid nothing from him.
    And he [Eli] said,
        It is the LORD: let him do what seemeth him good.
:19 And Samuel grew,
    and the LORD was with him,
    and did let none of his words fall to the ground. [what Samuel said came to pass]
:20 And all Israel
        from Dan even to Beersheba
    knew that Samuel was established to be a prophet of the LORD.
:21 And the LORDappeared again in Shiloh:
        for the LORD revealed himself to Samuel in Shiloh
        by the word of the LORD.

God has not changed. If we are hungering and thirsting God will fill us. God taught Samuel directly because there wasn't anyone else to do the job.  When there are instructed spiritual leaders available to you that know the rightly divided Word of God and walk accordingly they can instruct you. Still, it is a walk with Him. Communication is not just one person talking, expect replies. 

Samuel is considered the last of the Judges or the first of the great Prophets; a transitional figure. Eli was the man of God giving Samuel instruction, but God taught Samuel how to walk with Him. In reading I Samuel we will learn about Word of Knowledge.