There are 11 things Wajib in the Prayers:-

1. Niyyat:- Offer prayers with the intention of complying with the orders of the Almighty Allah.
2. Takibirat-ul-Ihram:- To say Allahu Akber (in the beginning of every prayer is obligatory).
3. Qiyam:- To stand erect while saying Takbiratul Ehram, and to stand before the Ruku.
4. Ruku:- After Quir'at, bow to an extent that he is able to rest his finger tips on his knees.
5. Two Sajdahs:- Sajdah means that one should place one's forehead on earth in a special manner, with the intention of humility (before Allah).
6. Quir'at:- to recite Sura Al-hamd and another Sura in the first two Rikats and Tasbihat-e-Arbaa in the third and fourth Rikats.
7. Zikr:- to recite tasbih in Ruku and Sajdah.
8. Tashahhud:- In the second unit of all obligatory prayers, and in the third unit of Maghrib prayers and in the fourth unit of Zuhr, Asr and Isha prayers, one should sit after the second prostration with a tranquil body, and recite tashahhud thus:
   "Ash hadu an la ilaha illal lahu wahdahu la sharika lah, wa ash hadu anna Muhammadan 'Abduhu wa Rasuluh, Alla humma salli 'ala Muhammadin wa Ali Muhammad".
   And it will be sufficient if one recited the tashahhud this way:
   "Ash hadu an la ilaha illal lahu was ash hadu anna Muhammadan Sallal lahu Alayhi Wa Aalihi Abduhu Wa rasuluh".
9. Salaam:- While a person sits after reciting tashahhud in the last Rak'at, and his body is tranquil, it is Mustahab to say:
   "Assalamu 'alayka ayyuhan Nabiyyu wa rahmatullahi wa barakatuh".
   Then he should say:
   "Assalamu Alaykum"
   and as a recommended precaution add to it
   "Wa Rahmatullahi Wa Barakatuh".
   Alternatively, he can say:
   "Assalamu Alayna Wa Ala Ibadi llahis Salihin".
   But if he recites this Salam, then as per obligatory precaution, he must follow it up with saying:
   "Assalamu Alaykum".
10. Tartib:- To pray in the sequence prescribed by the Shariah. (If a person intentionally changes the sequence of the prayers, for example, if he recites the other surah before reciting Surah al-Hamd, or performs the two Sajdah before Ruku, his prayers are void.)
11. Muwalaat:- To pray without interruption or gap. (If a person allows an undue interval between different acts, till it becomes difficult to visualise that one is praying, his prayers will be void.)

Note:
Qunut:- It is Mustahab that qunut be recited in all obligatory and Mustahab prayers before the Ruku of the second Rak'at.

Tasbihat Arba'ah:- In the third and fourth Rak'ats of prayers, one may either read only Surah al-Hamd or Tasbihat Arba'ah - which may be said once, although it is better that it should be said three times. It is also permissible to recite Surah al-Hamd in one Rak'at, and Tasbihat Arba'ah in the other, but it is better to recite Tasbihat in both.

RUKN AND GHAIR RUKN:

Out of the above mentioned Wajibs of Namaz, 5 are Rukn and others Ghair Rukn.



These are:

1. Niyyat
2. Takbiratul Ihram
3. Qiyam at the time of Takbiratul Ihram and just before going to Ruku
4. Ruku
5. Both Sajdahs together. If any of these are left out, or added whether intentionally or unintentionally, Namaz will become Batil.