The Rebbe's guidance on the mezuzah, especially when moving into a new home:
Moving into a new home. Moving is an opportunity for increased blessing (IK 2172, 8040). Affix all the mezuzos immediately upon moving in (IK 3182, 4443), and mark the move with a chanukas habayis in the customary way (IK 8040, 3182); on timing and customs of moving, see IK 7388.
Placement. On the order of affixing mezuzos, see IK 4311. According to Chabad tradition, the side of the doorway is determined by the door's hinges, with the "heker tzir" as a consideration (IK 4251, 7324); on other placement questions, see IK 4237, 6675.
Mezuzah and blessing. Kosher, properly placed mezuzos are part of the spiritual steps that go together with medical care and bring blessing and protection to a home (IK 5707). On checking mezuzos, see Health – Checking tefillin and mezuzos.
See also: Health – Checking tefillin and mezuzos; Livelihood – Buying a home, property and investments.