Looking Back at the Law of Moses concerning the issue of marriage I think it is safe to say we can make the following observations:
1. In many ways marriage can be defined in the Law a a contract between a man and a woman for the purpose of having and raising children.
2. This definition is significantly different from the idea of a man and woman becoming 'one flesh'. To be husband and wife in this sense goes a little beyond just having a contract to have children. The idea of being open and intimate with each other start right at the beginning 'naked and unashamed' is what Adam and Eve were before sin enters the picture.
3. As human history unfolds, the nature of marriage changes in many ways. a) Very quickly on we realize incest as we know it must not have existed because Cain and Seth would have had to marry their sisters, but at this time this is not forbidden by the law. Only later is the idea of incestuous marriages introduced by the Law. b) Polygamy is introduced very early one as an acceptable form of marriage. It becomes one of the chief characteristics of many of the characters in Genesis -- Lamech, Abraham, Jacob and Esau all follow this model. In some senses polygamy almost seems to a necessity in the producing of children in case the first couple fails to conceive, the handmaiden can be brought into the mix to produce a child.
4. Marriages are often arranged by others. There is little of romantic love involved. This is not a bust however as many of the arranged marriages work out.
5.One issue is intermarrying between the godly lines and the ungodly ones. The results are often disastrous so in the end the Law forbids the children of Israel from intermarrying.
6. One law that puts an interesting wrinkle on things is the law of an older brother's seed being preserved through a younger brother. It really brings home the 'sexual contract' only view of marriage.
7. Another Law is the law that requires a man to marry a woman if he seduces her and in so doing gives up his right to divorce.
8. That brings about the issue of divorce -- marriage as contract whose obligations can be set aside by the husband.
The thing that is sure is that at the beginning you have a situation where marriage does not exist so much as two people become one flesh but once sin enters it seems necessary to provide marriage as a way of enforcing the idea. This contract idea begins to express itself in different ways but always culture intrudes to bury the original intent of 'husband and wife".
Next: Giving Brides as Prizes
Arranged Marriage. To many Westerners such a concept is repugnant but in the ancient Near East and in much of the world today it is actually the most common way a couple gets married. When you get down to it though this would cut through a lot of the garbage associated with 'finding the one".
Now one thing that is often overlooked is that Abraham too was a polygamist but through a new concept at this point in the Bible -- concubinage. In the first case Hagar is offered to Abraham by Sarah (I always like to point out to people this was Sarah's idea). In Abraham's day this was common practice if the wife could not produce an heir, always nice to have a backup womb. Now we might argue that this was them not acting in faith. Maybe so but for the rest of Hagar's life she is considered to be Abraham's concubine/wife. In addition this is not the only concubine Abraham will take. After Sarah's death in Genesis 25, while Issac is being comforted by his new wife, Abraham takes a second concubine -- Keturah. She bears Abraham six children. Hagar is still alive. Two concubines for Abraham and the second one is by his own choice. 
You know for all the talk of how Issac was the child of promise and he is, one of the interesting things about his parents Abraham and Sarah was that they had the same father. Two different mothers (another polygamist relationship) but they were brother and sister as well as husband and wife. Incest by the time Moses writes the Law but at this point apparently there is no such thing.
Probably one of the most significant things about about the story of Lamech is his belief that God protected him because he was somehow greater than Cain even though he had murdered two men, although based on what he says is could have been self defense. In any case, that is not what is significant for this discussion. What is significant is Lamech is the Bible's first recorded polygamist. This introduces polygamy very early into our discussion on marriage.
It is an interesting question because we have certain notions of what it means when people get married but in the story of Creation none of those notions really exist: No ceremony, no vows, no license with a civil authority, etc. 
