Please bear in mind that the following is a general overview; much depends on whether a ceremony is to be reiligious, spiritual, or humanist, traditional or contemporary, and what you intend to add in the way of rituals or special ceremony.
Prayer, invocation, or words of welcome and settling people in mind and heart
Outlining the purpose of the ceremony
Song hymn, poetry or other reading if applicable
The Minister's address to the couple on the subject of marriage - this is NOT a sermon but is drawn from your ideas for the ceremony and any background information you have given
Stating of your intentions (confirming "do you --- take --- to be" etc)
The taking of your vows
The ring ceremony - outlining the purpose, symbology of exchanging rings, and then the blessing and exchange of the rings
Where appropriate, a joint prayer by the couple
The signing of a register (if desired; please note - this carries no legal significance but some couples like this to make the ceremony look "complete")
Inclusion of any ritual eg the candle ceremony, the rose ceremony, the couple's first exchange of a gift ceremony, or anything that may be specific to a particular religion or faith tradition
A (further) song, hymn, or reading (if desired)
Final prayer (if appropriate)
Main blessing of you the couple and pronouncement of you as husband and wife, wife and husband.