If all your documents are in order, it could be a very simple, cordial interview. Answer any and all questions truthfully but don't "give away" any information not asked for. (This is often referred to as "answer the question you're asked and only that question.")
If there are any sticky points about your relationship and/or marriage, make sure you have documentation with you covering anything that might cause problems, but don't offer it unless asked about it.
Generally, the better prepared you are for any and all issues, the less likelihood you'll actually need any of the extra documentation.
Cheers,
Bev