(This Halacha was delivered by a guest Rabbi, Rabbi Yinon Yona, chief Rabbinical supervisor over Mikva'ot in Israel, and author of the Hebrew work "Yemei Tohar," which was recently translated into English.)
The Shulchan Aruch (14:2) rules that when one makes Tzitzit, he must ensure to insert the strings in the holes of the garment with the specific intention that he does so for the sake of the Mitzva of Tzitzit. One must therefore say the words "Le'shem Mitzvat Tzitzit" ("for the sake of the Mitzva of Tzitzit") before he inserts the strings into the holes. Many people are unaware of this Halacha, and recite "Le'shem Mitzvat Tzitzit" only after inserting the strings into the hole, before tying the knot. If one did not have this intention when inserting the strings into the hole, the Tzitzit are not valid for use for the Mitzva, and he must therefore untie the Tzitzit, remove them from the hole, and insert them anew. This is also the position of Chacham David Yosef, in his Halacha Berura.
As mentioned, many people are unfamiliar with this Halacha; it is therefore critically important to purchase one's Tzitzit from somebody whom he knows is familiar with the detailed Halachot relevant to the tying of Tzitzit onto the garment.
In his presentation of the laws of Tefillin, the Shulchan Aruch (25:5) lists the various intentions that one must have when donning Tefillin. One must have in mind that he places the four Biblical sections contained in the Tefillin (Shema, Ve'haya, Kadesh, Ve'haya) near the brain, where a person's Neshama (soul) is located, and near the heart, where a person's desires originate. By placing the Tefillin near the brain and heart, one expresses the subjugation of his mind and desires to the Divine Will. In addition, a person should have in mind the Almighty's unlimited power, the miracles He performed for us in Egypt, as well as the notion of Hashgacha God's direct supervision and providence over everything that transpires in the world.
If a person did not have these intentions before he placed the Tefillin Shel Yad, or if he is rushed for time, he may think of these ideas as he wraps the strap around his arm.
The notion of subjugating one's mind to God is a particularly meaningful and important one. It means that all of a person's thoughts must precisely correspond to the Torah. Any idea that is contrary to the Torah's laws and values may not even cross a person's mind; the mind must be completely subservient to God, and must therefore be clean of any thoughts that run in opposition to His will.
Summary: 1) A person who ties Tzitzit to a garment for the Mitzva must declare before he inserts the strings into the hole of the garment that he does this specifically for the Mitzva of Tzitzit. 2) When a person dons Tefillin, he must have in mind that by doing so he subjugates his mind and his heart all his thoughts and desires to the Divine Will, and he should also think about God's unlimited power and His providence over the world. If one did not have this in mind before he donned the Tefillin Shel Yad, he should do so as he wraps the strap around his arm.
