Hey Guys--
Well, to the origial poster, this is the belief I have encountered w/ in the church in terms of your question:
On the eve of a major feast day and on Saturday evenings (when the Vigil to the Resurrection of Christ is celebrated each week), Orthodox Christian husbands and wives abstain from sexual relations in order that they can direct all their thoughts, actions and concerns to spiritual growth and not be occupied with non-spiritual matters. The Christian Church does not view sexual relations between husband and wife as a base act brought about by the sin of Adam and Eve for the sole purpose of conceiving children. The abstention from physical relations at these and other times is not motivated by a mentality that views these relations as unclean or sinful. The Church Council of Gangra held in 340 A.D. decreed four canons which uphold the respectability of the marriage bed.
Canon One states:If anyone disparages marriage, or abominates or disparages a woman sleeping with her husband, notwithstanding that she is faithful and reverent, as though she could not enter the Kingdom, let him be anathema. [42]
Canon Nine states:If anyone should remain a virgin or observe continence as if, abominating marriage, he had become an anchorite, and not for the good standard and holy feature of virginity, let him be anathema. [43]
Canon Ten states:If anyone leading a life of virginity for the Lord should regard married persons superciliously, let him be anathema. [44]
Canon Fourteen states:If any woman should abandon her husband and wish to depart, because she abominates marriage, let her be anathema. [45]
The abstention from sexual relations is for the sake of spiritual matters and preparation. This reasoning is as old as the Church itself, since St. Paul in his letter to the Corinthians (1 Cor. 7:5) indicates that husband and wife should not refuse each other except for times when they devote themselves to prayer.
-http://www.orthodoxinfo.com/praxis/xc_home.aspx
I haven't found or heard much else on the "specifics" except that everything must be done in love w/in the marriage act. I wont be explicit, but there are some sexual practices that are just not "loving." Anyway, I hope this thread remains peaceful and loving. I think this is a good question!