I have selected my wedding dress and this week I have an appointment to have measurements taken.  
1. Should I wear shoes of the same height that I will wear at the wedding? 
2. What measurements are involved? 
3. Will I be totally unclothed (except for Spanx and bra) as they take the measurements? 
4. Need I wear a strapless bra, or can I wear my everyday bra?
The wedding is 6 months away, so I have no idea what actual undergarments (type, size) I will be wearing under the dress except for Spanx.
Thank you!