The Barrow-Downs Discussion Forum

Well, I will be lazy so I'll just quote from the wondefully summed up article on Tolkien Gateway about marriage and sexuality among the Eldar:

Quote:

Elves marry freely and for love early in life. Monogamy is practised and adultery is unthinkable; they only marry once (Finwë, first High King of the Noldor, was an exception; he remarried after his first wife died). Spouses can choose each other long before they are married and be betrothed. The betrothal is subject to parental approval unless the parties are of age and intend to marry soon, at which point the betrothal is announced at a meeting of the two houses, during which the couple exchange rings. The betrothal lasts at least a year, and is revocable by the return of the rings (but is rarely broken). After their formal betrothal, the couple appoints a time for the wedding when at least a year has passed.
Marriage is celebrated at a feast of the two houses. The spouses return their betrothal rings and receive others worn on their index fingers. The bride’s mother gives the groom a jewel to be worn, but the marriage is only achieved with its consummation. Technically, only the words exchanged by the bride and groom (including the speaking of the name of Eru) and the consummation are required for marriage.
The Elves view the sexual act as extremely special and intimate, for it leads to the conception and birth of children. Extra-marital and premarital sex are unthinkable—indeed, the Elves would regard them as contradictions in terms. Because adultery is also unheard of and fidelity between spouses is absolute, spouses can sometimes live separately for extended periods of time. However, a sundering during pregnancy or during the early years of parenthood (caused by war, for example) is so grievous to the couple that they prefer to have children in peaceful times.
Elves have few children, as a rule; (Fëanor and Nerdanel were an exception, since they had seven sons), and there are relatively sizable intervals between each child. They are soon preoccupied with other pleasures; their libido wanes and they focus their interests elsewhere, such as the arts. Nonetheless, they take great delight in the union of love, and they cherish the days of bearing and raising children as the happiest times of their lives.
There seems to only be one known example of extreme marital strife among the Eldar: the case of Eöl and Aredhel, in which the latter actually left the former without his knowing, with the result of Eöl ultimately killing her. This was far from a normal Elven marriage, however.

By the way, in case you are wondering where this information comes from, the article is more or less a summary of a part of Tolkien's essay "Laws and Customs among the Eldar", to be found in volume X of the History of Middle-earth series "Morgoth's Ring".

If you also desire some direct quotes from the book I could try and search for some of the important ones, otherwise I strongly recommend you reading the essay itself in the book for a better understanding of this topic.

Hope this helped!