The Shulhan Aruch (Orah Haim 28) records the practice of the "Hachamim" to kiss the Tefillin as a sign of affection for the Misva when one puts them on and when removing them. There is, however, some debate surrounding this custom. It is clear that as one begins the process of laying Tefillin, after he takes his Tefillin Shel Yad from his Tefillin bag and before he puts it on his arm, he should kiss it, and then put it on his arm, recite the Beracha and tie it. It is unclear, however, as to whether he should also kiss his Tefillin Shel Rosh before placing it on his head. This issue is discussed at length by the Shela (Rav Yeshaya Horowitz, 1565-1630) who presents both sides of the argument. Some authorities say that one should not kiss the Tefillin Shel Rosh before putting it on his head, because this would constitute a Hefsek (inappropriate interruption), whereas others maintain that since kissing takes just a fraction of a second, it is not considered a Hefsek. And although the Shulhan Aruch writes plainly that one kisses the Tefillin when putting them on, implying that this applies to both the Shel Yad and the Shel Rosh, it is possible that he refers to touching the Shel Rosh after it is placed on the head and then kissing ones hand. He does not necessarily refer to kissing the Shel Rosh directly before placing it on ones head.
As for the final Halacha, Hacham Ovadia Yosef rules that one should not kiss the Tefillin Shel Rosh before putting it on his head, and he should instead touch the Shel Rosh after it is placed and then kiss his hand. Of course, when one removes his Tefillin, he should kiss both the Shel Yad and the Shel Rosh before rolling the straps and putting the Tefillin away.
Summary: When one puts on Tefillin, he should kiss his Shel Yad before putting it on his arm, but should not kiss the Shel Rosh before putting it on his head. Instead, he should touch the Shel Rosh after it is placed on his head and then kiss his hand. One should also kiss both the Shel Yad and the Shel Rosh when he takes them off, before rolling the straps.
