Most costumes need a full wash far less often than people assume. Sweat is the real enemy, and airing a garment properly after each wear does more for its life than washing it does.
Almost always glued. Heat and solvents are what release them, so keep the water cold, keep it away from the dryer, and never dry clean. Store flat rather than hung — a heavily stoned bodice is surprisingly heavy and will stretch its own shoulders over a season on a hanger. See Rhinestones.
Spangles are heat-set, so an iron will melt them outright. Sewn sequins snag on everything, including each other. Turn the garment inside out to wash, and keep it away from hook-and-loop fastenings in the bag. See Spangles & Sequins.
The dye is in the fibre, so it cannot crack or peel and it tolerates washing better than anything else on this page. It can still fade in prolonged direct sunlight — dry it in the shade. See Sublimation Printing.
Vinyl lifts at the edges when it is flexed hot. Cold water, no dryer, and never place an iron directly on it. If a corner starts to lift, deal with it before the next wear rather than after. See Heat-Pressed Vinyl.
The most robust decoration there is, because it is thread through fabric rather than something stuck on top. Its weakness is snagging — a pulled thread on a satin stitch runs. See Embroidery.
The most fragile part of most skating dresses. Fine mesh ladders like tights, and nude illusion yellows with age and with heat. Wash gently, keep it out of the dryer, and store away from anything with a hook or a zip.
Turn the costume inside out and hang it somewhere airy for a few hours. If it needs freshening, a light mist of equal parts water and vodka on the lining kills odour without wetting the decoration — it evaporates and takes the smell with it. Do not spray perfume or deodoriser onto a stoned area.
Losing the occasional stone is normal on a garment that has competed, and it is fixable. Keep the piece, note where the gap is, and have it re-set with a proper stone adhesive rather than a general-purpose glue. Craft glue yellows, and it will show under lights.