1. The woman/man is permissible to one another. i.e., that she is not one of those forbidden to him by relation, nursing or other existing and conflicting marriage. Some would consider this on of the Arkaan (pillars) or one of the conditions for initiating the contract. In any case, this condition must definitely be met.
2. The offer and acceptance is of a permanent nature and not temporary. All forms of temporary marriage are forbidden in Islam. If anything stated in the offer and acceptance indicates a temporary nature, the marriage is not valid.
3. Two non-discredited witnesses. There is some difference of opinion on this issue, but in the final analysis, the Hadith is clear. Ibn Taimia mentioned four existing opinions on this issue:
(1) The marriage must be announced and made public, regardless of whether the contract was actually witnessed or not.
(2) It is obligatory to have witnesses, regardless of whether the marriage contract is made public or not.
(3) Both witnesses and a public announcement are necessary.
"Laa nikaaha illa bi waliyin wa shaahidaiy 'adlin" "No marriage except with a guardian and two non-discredited witnesses."
So the bottom line here is that BOTH, the witnesses AND the public announcement are required.
4. Both parties to the contract and the bride have willingly accepted the marriage.
5. The bride and groom are specifically identified and known.
6. Neither of the two contracting parties are in a state of Ihram (Pilgrimage).
7. The marriage must be with a dowry (Maher). It does not have to be exactly specified nor does it have to change hands, but it has to be there.
8. The parties and witnesses are not bound to keep it quiet. It is not allowed to make attempts to keep a marriage a secret. The universal custom of the Arabs before Islam was to have marriages very publicly where all around became aware of its existence. Islam confirmed this practice and it is the only acceptable way of marrying. As we have seen, the Maliki School takes this so seriously that they separate the two parties permanently. Some other scholars said that it was a wrong practice, but didn't necessarily invalidate the marriage.
9. No party is on his/her deathbed. The "parties" intended here are the bride and the groom. This is because of possible injury to the heirs because of another person becoming entitled to inheritance.
10. The presence of the guardian or representative (Wali) of the woman. The Wali is a Muslim man charged with marrying the one under his charge to a man who will be good for her. There is no disagreement that the first Wali is her natural father if he is Muslim and that the last in line is the Ameer of the Muslim community. The order, according to many is: father, paternal grandfather, son, grandson, full brother, paternal half-brother, and paternal uncle.
It is the duty of the Wali to marry her to the best possible husband. He must not be guided by his desires or by her desires. If the person is acceptable in both his religion and his character and appropriate to her in some other way discussed by the scholars, then he must facilitate the marriage and not refuse it for his own desires or biases. If the conditions are not right, then he must refuse the marriage, even if both the woman under his charge and the man desire it. This is a grave trust and he must do his best to fulfil it properly and not bring harm to the woman and/or to society.