1. Make sure your costume is fully prepared way ahead of an event
All of us have been guilty of this at some point. It’s important to start your projects early (like, 3 months in advance at a bare minimum) so you won’t find your hands burned/bleeding/glued together the night before the con. Sure, sometimes it genuinely can’t be helped but it never hurts to start early whenever you can, especially if it’s something complicated. You seriously don’t want to be still finishing up that complicated sewing work or wig work the night before an event or convention. You’ll just end up with something sad looking or worse, incomplete.
Also don’t forget to figure out how to bring your stuff with you. It’s fine if your costume can be fitted into a suitcase or a coat cover but your more complicated projects might need a couple of boxes to bring over.
Being prepared for unexpected costume hiccups wouldn’t hurt either so you will want to assemble a repair kit. It can consist of basic things like scissors, sewing material, glue and maybe a roll or two of duct tape in-case things go sideways during the con. If you’re not alone and have a saikang/helper/entourage it’s even better, as you can get them to help carry your loot.