There shouldn't be any mysteries or grey areas before you start sewing. Plan what section you'll tackle first, second, and beyond. Special clothes for special occasions require something extraordinary in the way of fabrication. There is nothing more wonderful than marrying a design you adore with a fabric that you've fallen in love with. The inspiration that you've fallen in love with.
Fabrics look different under the fluorescent lights of a shop than they do in natural light.
Keep your work area clean. It is practically impossible to keep certain projects spotless for the entire time that they're being worked on, but avoiding trouble in the first place is the way to start. Be sure that your machine is free from any kind of surface oil or lint, and consider covering the area under your worktable and ironing board with old sheets. Be sure there's nothing rough for a gown to catch on. When your day's work is done, consider storing your project in a garment bag.