Jean asks, "My husband is already overseas (he signed the naturalization application before leaving) and I am planning to join him soon, but before that we want to mail our USCIS Form N400. How do we account for this trips or any other that might happen before the interview?"
The rule of thumb is that any trip that has not yet concluded need not be listed on the application. At the time of the interview, the officer will always ask if there have been any changes since the application was filed (it is a very important question and is always asked because change of marital status can make some applicants temporarily ineligible for naturalization) and you should have your information ready for submission (rather than trying to speak it out to the officer, it is smart to essentially type the information on a blank sheet of paper in the same format or simply reprint the update application that you must have). If the trip does change your eligibility in any way, it is only a matter of record.