Excerpt from 'Islamic Laws':
Issue 772: There are many Mustahab prayers which are generally called Nafilah, but more stress has been laid on the daily Mustahab prayers. The number of the Rak'ats everyday excluding Friday, is 34. ...
Fajr:
2 raka'ats for Fajr
Issue 780: * The Fajr Nafilah is offered before the Fajr prayers, and its time commences when Salat al-Shab has been completed, till the time of Salat al-Fajr draws near. But if someone delays it till redness is seen in the eastern sky, then it is better to pray Salat of Fajr.
Dhuhr:
8 raka'ats for Dhuhr (4x2)
Issue 776: * The Zuhr Nafilah is offered before Zuhr prayers. Its time is from the commencement of the time of Zuhr, up to the time when the shadow of indicator equals 2/7th of its length. For example, if an indicator is 7 yards long, and the shadow appearing after Zuhr reaches 2 yards, the Nafilah time would end. He should now offer Zuhr prayers.
Asr:
8 raka'ats for Asr (4x2)
Issue 777: * The Asr Nafilah are offered before Asr prayers, and its time is till the moment when the shadow of an indicator appearing after Zuhr, reaches of 4/7th of its length.
In case a person wishes to offer Zuhr and Asr Nafilah after their recommended time, he can offer the Zuhr Nafilah after Zuhr prayers, and the Asr Nafilah after Asr prayers, but as a precaution, he will not make niyyat of Ada or Qadha.
Maghrib:
4 raka'ats for Maghrib (2x2)
Issue 778: * The Maghrib Nafilah should be offered after Maghrib prayers, and one should make an effort to offer it in time after Maghrib. However, if one delays offering Maghrib Nafilah till redness in the western sky disappears, then it would be better to offer Isha prayers at that moment.
Isha:
2 raka'ats for Isha
Issue 772: ...As an obligatory precaution, the Nafilah for Isha prayers should be offered while sitting, and therefore its 2 Rak'ats are counted as one.
Issue 779: The time for Isha Nafilah is from the completion of Isha prayers till midnight. It is better to offer it immediately, after Isha prayers.
Shab:
11 raka'ats for Shab (4x2 + 2 + 1)
Issue 781: * The time for Salat al-Shab is from midnight till Adhan for Fajr prayers, and it is better to offer it nearer the time of Fajr prayers.
Issue 774: * All Nafilah prayers can be offered while sitting, but then, certain Fuqaha say that 2 Rak'ats prayed sitting should be counted as one Rak'at. For example, if a person wishes to offer Zuhr Nafilah which consists of 8 Rak'ats, in a sitting posture, he should offer 16 Rak'ats. And if he wishes to offer Witr prayers while sitting, he should offer two prayers of 1 Rak'at each. This later preference is not known from any sources; however, they may be followed with the hope of earning divine pleasure.
Issue 775: Zuhr Nafilah and Asr Nafilah should not be offered when one is on a journey, and one may offer Isha Nafilah with the intention of Raja'.