You could start with an overview of types of marriages as found in wikipedia.
Then you move on to the “Alambamento”:http://globalvoicesonline.org/2010/08/29/angola-alambamento-and-marriage-practices/ practice in Angola. The alambamento consists of a series of rituals, like the delivery of a letter with the request for the hand of the bride, which sometimes comes with money.
Then there are the Levirate marriage practices among the Yoruba, Igbo and Hausa-Fulani in Nigeria. Levirate marriage, where a family member inherits a married woman whose husband is dead, continues to be practiced under various customary law systems in Nigeria.
The Canela people of Brazil have interesting ideas about what incest is.
The Canela marry persons they consider to be “non-related” (ka?khrit), where the genealogical relationship has been lost: forgotten or very attenuated by social or spatial distance. All of ego’s kin (R-C mëhũũkhyê; A-C më?khwè), even out to third collaterals, and further if parallel cousins, may be considered “blood relatives” (mëi-kaprôô-khwè, my blood group), at least in theory. When these kin are of the opposite sex, they are considered unavailable for marriage or sexual purposes. They also sometimes “commit incest” (to ayprè) with relatives as close as third or second cross-cousins.4 First cross-cousin sexual relationships and marriages, which occur very rarely, are held to be shameful and life shortening. Uterine sibling sexual contacts are thought to cause madness or death.
And how about marriage in the Potawanomi Nation? A marriage was a relatively informal process in the old days. A man who wanted to marry a woman would make his intentions known by bring a gift, such as horses, to her parents. When the union was agreed to by both parties they would marry. The groom would go to the woman’s house where he would be stripped and given a new set of clothes.
The bride would then go to the man’s house and his female relatives would dress her in a new set of clothes. After these steps they would move into their own home.
Today they often use a pipe in marriage ceremonies. The joining of the pipe is symbolic of the joining of a man and a woman. Also a blanket can be wrapped around the shoulders of the new couple to signify a new union.
If you just google it, you will find hundreds… maybe even thousands of different marriage practices around the world. All have been studied by various anthropologists.