Simply put, an interfaith wedding is one in which both spouses profess different religions; this is also referred to as a mixed marriage. This is a blending of families, cultures, religions, and traditions all in one ceremony.
Planning an interfaith wedding can be joyous, but complex. Creating one unified family from two different viewpoints can be done, and done well. Things to consider before walking down the aisle might include these steps.
Take a course in your fiance's religion or attend their church or synagogue.
Even if you are not converting, it helps to see the world from their vantage point, especially if their faith is important to them or if they have different holidays than you do. For instance, people in the Jewish faith will celebrate Hanukkah, where Protestants will celebrate Christmas. Check to see if it's necessary for your fiance to be a member of your church before they will allow you to get married there if that is a consideration.
Get marriage counseling.
This should be a must do for all couples, but it might be especially helpful for those who profess different faiths. They might be able to help you foresee the unique challenges you'll face and help you work through them.
Include both faiths in the wedding.
You might have a wedding program that includes descriptions of the customs that your guests might not be familiar with. Find an officiant that understands your unique situation and is willing to conduct a ceremony that might be atypical. Many couples choose to have their ceremony performed by a non-denominational officiant in this case. You might also have two completely separate wedding ceremonies that you can do right after the other.
Embrace your new families' religion/culture.
Know that who they are is in part rooted in where they came from and the religion they adhere to. Don't expect your spouse to give up their heritage, culture, and practices the day you share the same last name.
This should probably go without saying, but make sure your family is aware of your fiance's background. The wedding is not a good time to ambush them and hope for the best. In fact, make sure that everyone in charge, from the wedding planner to the officiant, to the attendants, know exactly what you want in the wedding and reception so that they can help head off any potential confusion.