If you're shooting content: pick fishnet or mesh with dense stone coverage. More stones means more sparkle on camera, and an open weave photographs better than solid fabric under a ring light.
If you'll wear it for hours: choose soft mesh over stiff fishnet. Stiff fishnet can press a grid pattern into your skin over a long night. Soft mesh moves with you.
If you're between sizes: size by the stretch, not the letter. Fishnet has a lot of give, so the smaller size usually works. Structured pieces like bustiers need your real bust and waist measurements.
If it's a gift: go for a thong or a stretch fishnet piece. Both cover a wide range of sizes, so a guessed size is less of a gamble.
If you're heading to a festival too: pick a set that works as outerwear. Rave sets cover the festival and the bedroom in one purchase.
Keep heat away from the stones. Hand wash cold and lay flat to dry. A dryer or iron loosens the glue behind hotfix rhinestones.