Christine Klapisch-Zuber discusses upper-class wedding ceremonies in 14th-15th century Florence in her book Women, Family, and Ritual in Renaissance Italy, if you think that time, place, and social class would offer a useful model.

The first thing to keep in mind is that later medieval Italy, especially urban Italy, is the place in medieval Europe where the disparity in marriage age between male and female was the greatest. Although at this time we are seeing nearly equal marriage age in the late teens and early 20s in the northwest European cities, Italian cities see very early marriage for girls (young teens) and late 20s/even early 30s for men, who often were still living in their fathers' homes to maintain the paterfamilias wealth all in one place. Marriage marked, essentially, the transition of a girl from her father's home into her father-in-law's.

Klapisch-Zuber takes a very pessimistic view of the status of women in the late Middle Ages; other scholars have a more positive view. So keep that in mind as I convey her relation (interpretation) of marriage events.

Under medieval canon law, the definition of a valid marriage was consent by the two parties. In urban Italy (even more so than elsewhere), that essentially meant parental consent. A marriage broker would actually be hired to make the initial contact and dowry negotiations between the two sets of parents. (In Florence, fathers used to advertise their daughters for marriage, right down to lying about the age of their older daughters in an effort to secure more favorable dowry terms, i.e., have to pay less to get the husband's family to take their unmarriageable daughters off their hands.) Once the broker had negotiated the terms, the men of the families would meet to make the deal official. Often this took place before the girl was old enough to marry (12 according to canon law).

The marriage ceremony itself typically took place in the girl's family's house, with as many of her and his extended kin present as would fit. The ceremony was performed by a notary deputized by the Church, usually someone with clerical training but not ordained, who would ask a series of questions about fidelity and religion required by the Church. Unfortunately, I don't have a list of these questions or a formal marriage liturgy to hand. (I did TA for a prof who used a Latin-language medieval English marriage rite at his own wedding, because of course he did, so I know they exist somewhere.) After that, the new spouses would offer their formal consent to marriage in front of witnesses.

There was a massive exchange of gifts. I'm not clear whether this took place during the ceremony, or afterwards at the groom's house. At any rate, the couple would first of all exchange rings. In return for the dowry of cash and goods that the wife's family was obligated to pay the husband's, he would be responsible for burying her under gifts of his own. The female members of the groom's family would also give the new wife rings and other jewelry to mark her entrance into their family. These rings, however, were not true gifts--they still belonged to the patrilineage. If the husband died and the now-widow returned to her father's house (we do not see independently powerful widows among the Italian upper classes), she would have to leave behind the rings and, tragically, her children.

Finally, a public announcement would be made. This might occur right after the ceremony. Or it might take place the next weekend, when the new couple attended Mass together for the first time.

In between, of course, was the great Italian wedding ritual or the mattinata. You may be familiar with the term charivari, which is the generic phrase for a mock serenade; this one is wedding specific. It was a way for the husband's family and friends to be included in the wedding "pact", but could also serve a double purpose as a chance to vent community frustration over a pairing (such as when a widower married a widow, which was not a popular situation in super-Christian, medieval/Catholic style, Italy). This is the loud parade through the streets and outside the couple's family's house and bedroom window.

I highly recommend the work of Klapisch-Zuber and her sometimes-collaborator David Herlihy on the social history of Italy, especially Tuscany. If you have a more specific context in mind, let us know--we actually have multiple medieval Italy specialists in AskHistorians (my research is elsewhere, but I joke that my flair really should say "MEDIEVAL SEX" given what I tend to write about on AskHistorians).

Good luck!