When praying, do everything with understanding. When you pour oil into the lamp burning before an icon, represent to yourself that the Life-giver every day, every hour, every minute supports your life by His Spirit, and, as daily by means of sleep in bodily respects, through prayer and the Word of God in spiritual respects, pours into you the sacred oil of life, by means of which your soul and body burn. When you place a candle before an icon, remember that your life is like a burning candle, that it will burn out and be extinguished, or that some other reasons, such as the passions, surfeiting, wine and other pleasures, make it burn faster than it should.
During prayer, before the icons or without them, it is necessary to always have full hope of receiving that which we ask for — for instance, deliverance from afflictions, spiritual sickness, and sins, because we have already a thousand times experienced that we do clearly obtain mercy from the Lord or Our Lady; and therefore, not to hope to obtain that which we ask in prayer, or to doubt in the fact of our prayers being heard, would be the greatest foolishness and blindness.
It is an excellent custom with Christians, and one pleasing to God, to have an icon of the Saviour and to pray to Him before it. This is a crying necessity of our soul. The Lord Himself, with the love which is proper to Him, desires to be formed in us, as the Apostle says: "My little children, of whom I travail in birth again until Christ be formed in you"[1230] ; or "that Christ may dwell in your hearts by faith."[1231] But how can I form Christ in my heart if I do not first represent Him sensibly before my eyes? Thus we have images of the Saviour, of the Mother of God, and others. The love of Christians for them, desiring to always carry their images in their thoughts and hearts, as well as our nature, which is both carnal and spiritual, has called forth the necessity of representing Them on painted icons, placing them in the most honoured places of the house, as in our hearts or the chambers of our soul, and of reverencing them by bowing to them, first spiritually, and then bodily. And how in accordance with God's intention our veneration of icons is! Heaven itself replies to us from the icons, as the Lord in olden times replied from the mercy-seat in the Hebrew tabernacle; many of them shine by miracles.
Every place is the place of God's presence and sovereignty. Hence it is undoubtedly true that the Lord looks upon us with the eyes of the holy icons as with His own, and can speak to us by the mouths of the holy icons as by His own. Also, owing to the fact that the Lord is in every place, His cross, His name work miracles. His icons show themselves to be wonder-working, and are in every case places of His gracious presence.
An Excerpt from the diary of St. John of Kronstadt On Holy Icons, Images and Symbols.
http://agapienxristou.blogspot.ca/2013/04/praying-before-icons.html