Make a list of assumptions that will be used as the basis for planning the wedding.
And no, it is not acceptable to assume that Tony and Peggy Sue will just elope, no matter how tempting that may be!
Develop a work breakdown structure.
Make a list of the specific activities that need to be done between now and the wedding day.
For each activity, identify the person (Tony, Peggy Sue, etc.) who will be responsible for seeing that the activity is accomplished.
Create a network diagram that shows the sequence and dependent relationships of all the activities.