Marriage customs vary widely between countries and cultures, although there are definite regional trends.
Among the Aiel, marriage is instigated by the woman who crafts a bridal wreath which reflects her personality and lays it at her intended's feet. Usually she already knows that he will accept, especially since there is no prohibition against having more than one wife among Aiel. Women who become related in this fashion are described as sister-wives.
In Ebou Dar and other parts of Altara, when a woman gets married she receives a marriage knife from her new husband. There is a cultural expectation that she may (and should!) stab him with it if he ever displeases her. Throughout her life, the knife will gain additional decorations reflecting her children, marital status, etc.
Altarans recognize the "right" to have a pretty, a young and beautiful lover, prior to marriage. Both women and men will fight duels over potential or current lovers however, although married and widowed women are challenged less often than single women or any men.
Andoran marriage customs reflect the general standard of the Westlands; most men and women marry after a time of courtship, while nobility may be forced to marry for political reasons.
In the local area of the Two Rivers, it is expected that young men and women will refrain from serious courtship or flirting until they are "mature enough"; at that point women may braid their hair and dance around the Bel Tine pole, and men may start to court women in earnest.
Engagements are a long affair, even after the Women's Circle agrees; they typically last more than a year, although they are sometimes "rushed" to avoid the embarrassment of an out-of-wedlock birth, or similar circumstances.
Among the Atha'an Miere, marriage is designed in all circumstances to be egalitarian; since changes of rank and responsibility change often, a woman may be her husband's superior on board a ship one year, and his subordinate another. Because of this, they hold strictly to a balanced power structure: whoever is in charge in public submits to their spouse in private. 
Atha'an Miere also expect newly married couples to consummate the relationship on the first night, or it may be considered invalid.[verify]
More significantly, Malkier had a formal custom of granting a person's first lover, or carneira, special rights and authority over them while they are in that relationship. Young women choose their own carniera, while women choose the young men they wish to train. The intended braids their hair into a long rope (daori), which so long as they hold in their hands gives the carneira total control over them in the bedroom.
Mayeners in general appear to have a more relaxed attitude toward sex and marriage than most people of the Westlands; politically-motivated liaisons are endorsed and used without much comment, and Berelain notes without shame that she has had three lovers, while never having been married.
However, one unusual custom allows for an 'instant marriage' if both parties describe the other as their husband/wife in front of witnesses. There are other blessings and formalities, usually, but the exchange of affirmations suffices for a binding marriage vow.