Jewish Law (Halacha) does not require that a rabbi officiate at a Jewish wedding ceremony, as the marriage is seen as essentially a private contractual agreement between a man and a woman. Nevertheless, it is common for rabbis to officiate at wedding ceremonies today.

While a rabbi is not mandatory, Jewish Law does require that at least two witnesses, unrelated to the couple, attest that all the aspects of the marriage occurred.

The Sabbath prior to the wedding, it has become customary in the synagogue to call the groom up to bless the Torah during prayer services. The groom’s blessing of the Torah (aliyah) is called an Aufruf. This custom conveys the hope that Torah will be a guide for the couple in their marriage. It also provides an opportunity for the community, what generally sings “Mazal Tov” and throws candy, to express their excitement about the upcoming wedding.

The day of the wedding, it is customary for the bride and groom to fast. They also recite psalms and ask God for forgiveness for their transgressions. Thus the couple enters into their marriage fully cleansed.

Before the wedding ceremony itself begins, some grooms will veil the bride in a ceremony called Badeken. This tradition is based on the Biblical story of Jacob, Rachel and Leah.

Next the bride and groom are escorted to a marriage canopy called a Chuppah. It is believed that on their wedding day, the bride and groom are like a queen and king. Thus, they should be escorted and not walk alone.

Now under the Chuppah, the bride circles the groom seven times. Two blessings are then recited over wine: the standard blessing over wine and a blessing related to God’s commandments about marriage.

Next the groom places the ring on the bride’s finger. As he puts the ring on her finger, the groom says “Be sanctified (mekudeshet) to me with this ring in accordance with the law of Moses and Israel.” The exchange of the wedding ring is the heart of the wedding ceremony, the point at which the couple is considered to be married.

Next the Ketubah is read out loud. And then the groom gives and the bride accepts the Ketubah.

It is customary to conclude the wedding ceremony with the recitation of the Seven Blessings (Sheva Brachot), which acknowledge God as the creator of happiness, human beings, the bride and the groom.

After the blessings have been recited, the couple drinks wine from a glass, and then the groom breaks the glass with his right foot.

Immediately after the Chuppah, the married couple goes to a private room (Heder Yichud) to break their fast. Going to the private room is a symbolic consumation of the marriage, as if the husband is bringing the wife into his home.

It is traditional at this point to have a festive meal with music and dancing.

Source: http://judaism.about.com/od/weddings/a/all_marriage.htm