The Position of One's Limbs at the Time of Prayer, containing 4 s'ifim
One should position one's feet next to each other as though they are one, in order to imitate angels, as it written regarding them: “their feet were a straight foot” [(Ezekiel 1:7)], which is to say their feet appeared as one foot. (Some say when one stands to pray one should take three steps forward in the way of coming close and approaching a matter that must be done.) (Rokeach)
One should bend one's head a little so that one's eyes will be downwards to the ground and one should consider oneself as if one is standing in the Beit Hamikdash, and in one's heart, one should direct [oneself] upward towards the heavens.
One should place one's hands over one's heart, as if bound (i.e. as if connected), the right [hand] over the left, and stand like a servant before one's teacher with terror, awe, and fear. And one should not place one's hands on one's hips, because that is the way of haughtiness (and see below in the beginning of Orach Chayim 97).
It is proper to position one's feet [together] also at the time one is reciting Kedushah with the prayer-leader.