Since my lovely new ballgown is currently ready for action, let's talk about a few things that keep those costumes ready to dance. Regardless of your style or gender, your competition clothes are going to get damaged after being danced in. Seams pop, skirts and floats get stepped on, buttons pull off, and decorations come loose. Hence you should keep a small sewing kit with your costumes.
You can see above the sewing supplies I bring to a dance competition. The needles, thread, and scissors are for dealing with small rips or popped stitches. The safety pins are for holding things together when you're about to walk out on the floor, or in a pinch for my partner's number. The black thread is for my husband, since we pack these things together. This advice applies to men as weell. Buttons on the fronts of tailsuits are unfortunately right about where the lady, in her stoned and decorated dress, makes contact with her partner; they need to be re-enforced or they will disappear, probably right before you dance a final.
You should also check your costume for damage regularly, and correct things as soon as possible. I can attest that I have sat backstage at a competition, in costume, with needle and thread repairing a hole in a seam. After all the money and effort that goes into our costumes, it is worth it to protect the investment.