The following Three pre-conditions must be full-filled for all acts of worship in Islam.
Islam is the Faith
In order Salah to be acceptable, one must be a muslim in failth
Sanity
The person should be sane, the insane person are not required to perform salaat
O ye who believe! Approach not prayers with a mind befogged, until ye can understand all that ye say,- nor in a state of ceremonial impurity (Except when travelling on the road), until after washing your whole body. If ye are ill, or on a journey, or one of you cometh from offices of nature, or ye have been in contact with women, and ye find no water, then take for yourselves clean sand or earth, and rub therewith your faces and hands. For Allah doth blot out sins and forgive again and again. [<a style="color: teal; font-weight: bold;" onclick="open_evidence_on_modal('/index.php/evidence/view/563/1');" > Al-Quran </a>]
Maturity of Age
The person should have reached the age of disctinction (7-10 years old minimum) when he/she can judge between right vs. wrong and between True vs. false.
Conditions before conducting Salah - Shoroot A-Salah (the prerequisites of the Salah):
The obligations that need to be fulfilled before one starts the Salah. Absence of any of these invalidates Salah. To validate, salah must be repeated after fulfilling these opbligation.
Please see the section Pre Requisites for Salah > Before Conducting Salah for more details about this topic.
Examples: Performing Wudu, Facing the Qiblah etc.
Conditions while Conduting Salah:
Arkan As-Salah (the essential components of the Salah)
Arkans (singular: Rukun) are the obligatory actins required within the Salah. Salah is invalid if intentionally skipped any of these actions during Salah. Intentionally missed Arkans cannot compensated using prostrate for Sahw (forgetfulness). Salah Must be repeated to include the missing action.
If he leaves out one or more Arkan(s) by forgetfulness, then he has to make it up and prostrate for Sahw (forgetfulness) after Tasleem. Please see details in the section Mistakes and Forgetfulness in Salah.
Wajibat As-Salah (the obligatory elements of the Salah)
Salah becomes invalid if any of these actions are intentionally skipped during Salah.
However, in case of forgetfulness Missed actions can be compensated using prostrate for Sahw (forgetfulness) before Tasleem and there is no need to repeat the Salah if compensated using prostrate for Sahw.
Sunnan As-Salah (the recommended acts of the Salah)
Recommended actions in the Salah. Absence of these actions does not invalidate Salah, however they are highly recommended actions those are practiced by the prophet (صلى الله عليه وسلّم) .
However, if one intentionally leaves out a Rukun or a Waijb, then his Salah is invalid.
A detail list of all actions of conducting Salah and their related condition is listed in section: Conducting Salah - Summary > Summary Of Activities