The Nikah is a sacred and special ceremony that binds a man and a woman together as husband and wife under the eyes of Allah. It is a simple process that involves a contract between the husband and wife. Once agreeing to the contract, both parties must do their utmost to fulfill their duties to each other, to Allah(swt) and to their kith and kin. The laws in many Muslims countries these days requires the nikah to be conducted by a recognized official, be it an imam. This is to safeguard the legal validity of the marriage and to make sure the proper paperwork is issued.
For Nikah to be valid, there are some conditions that must be fulfilled.
The Woman has to agree to the marriage, Some practices call for the woman to be asked if she agrees to marry a certain man. She should say "yes" or keep silent, which implies agreement. A woman cannot be forced to marry anyone.
Guardian - A nikah is not valid without the consent of the male guardian, or wallee. This is usually the woman's father, or it can be male mahram. If no wallee can be found, the imam can act on the woman's behalf.
Two witnesses - Two trustworthy witnesses, generally males, must attest to the nikah. Some Muslim societies require two witnesses each from the groom and bride's sides in addition to to unrelated witnesses, making six in all.
Mahr – the groom’s side must offer a certain amount of mahr, or dowry. This could be in the form of cash, jewelry or other items of value, as long as the bridge agrees. The mahr does not have to be physically handed over to the woman at this stage but a contract of intent must be sealed for the marriage to be valid..