When to Pray Fajr Sunnah?
Question

How should the prayer before Fajr be offered so that it will be counted as one of the twelve regular Sunnahs? Here in Morocco they give the Adhan for Subh then we get up and pray Fajr then Subh. We hope that you can explain to us when we should pray the two Rak`ahs of the twelve regular Sunnahs, especially the two Rak`ahs before Subh.
Praise be to Allah.Twelve optional prayers
The twelve regular Sunnahs , concerning the virtue of which it is narrated that the one who offers them regularly will have a house built for him in Paradise, have been explained in the answer to question no. 1048 . 
They are: the two Rak`ahs before Fajr, four Rak`ahs before Dhuhr and two Rak`ahs after it, two Rak`ahs after Maghrib and two Rak`ahs after `Isha. 
When to Pray the Sunnah of Fajr 
What you do after the Adhan for Subh and before the obligatory prayer is supererogatory and they are the two Rak`ahs of Fajr which are called the Sunnah of Fajr or the Sunnah of Subh . They are among the twelve regular Sunnahs, as mentioned above, and your doing them is part of regularly observing this regular Sunnah. 
For more details, please see the following answers: 65746 , 136695 , 150006 , and 33779 .
And Allah knows best.