The choice of an appropriate spouse ensures a good foundation for the family they will establish. For this reason, Islam pays great attention to the way one chooses a spouse. In choosing a bride one should take into consideration his preferences regarding her physical beauty and character, but most importantly he should seek a Muslim woman of high moral and religious standards. The Prophet (SAW) said:
"A woman is normally sought as a wife for her wealth, beauty, nobility, or religiousness, so choose a religious woman and you will prosper." (Related by Muslim)
"When someone with whose religious and character you are satisfied, asks to marry your daughter, accede to his request. If you do not do so, there will be corruption and great evil on earth." (Related by Al-Tirmidhi)
* It is unlawful for a Muslim to marry a woman who is a Mahram to him. Also, he should not propose to a woman who is actually married; a woman who is in her Iddah (the waiting period of the divorced or widowed woman); a woman whom another Muslim man has already asked in marriage - unless she has already refused the first or if he permits him; a disbeliever, with the exception of chaste (virgin) Jewish or Christian women; a prostitute (unless she has repented from it sincerely). It is also unlawful for a Muslim woman to marry a non-Muslim man.
* It is preferred, though not obligatory, to avoid choosing a wife among close relatives. Allah (SWT) said:
"We have created you from a male and a female, and made you into nations and tribes, that you may know one another." (Al-Hujurat 49:13)
"Marry the fertile, affectionate women, for I want you to outnumber other nations (on the Day of Resurrection)." (Related by Abu Dawud)
* The wali should make sure the man who is asking to marry the woman is of sound religion, and is capable of supporting her.
* The wali should seek the woman's consent before accepting the offer of the proposing man. The Prophet (SAW) said:
"A woman who has been previously married has more right concerning her person than her guardian, and a virgin’s consent must be asked about herself, her consent being her silence."
(Related by Al-Bukhari and Muslim)
Here is a great story during the time of the Partition of India regarding this issue.