Get your Mezuzah Ready
Just before you affix the Mezuzah you say the traditional Mezuzah blessing. You can say it in Hebrew or translated to any language you understand.
First get the Mezuzah in position with your nails ready or the double sided tape peeled. Make sure you know how high and on what side of the door you want to affix the Mezuzah. When you are all ready, say the Mezuzah Blessing and then immediately, without talking, affix the Mezuzah.
The Mezuzah Blessing
Here is the Mezuzah Blessing in Hebrew, transliterated to English and in English: