The basic advice given for all jewelry in jewelry care also applies to jewelry made with Swarovski crystals.
Keeping crystal jewelry clean and shiny starts with avoiding exposure to chemicals such as hairspray and perfume. Such chemicals can build up on the crystals and make them look dull. When dressing always put your crystal jewelry on last, after you've applied makeup, lotions and sprays. Remove your jewelry first when undressing.
After you take your crystal jewelry off, wipe gently with a damp cotton cloth to remove oils and fingerprints. If your crystal jewelry needs additional cleaning, dip a cotton swab into water containing a few drops of window cleaner and lightly wipe any problem spots off specific crystals with that. Lay your clean crystal jewelry on a cotton cloth to air dry, overnight if possible.
When your crystal jewelry is thoroughly dry, wrap in jewelers' tissue and store in its own airtight plastic bag. Keep it separate from other jewelry so it doesn't get scratched or scratch your other pieces of jewelry.
Many styles of Swarovski crystals have a thin coating on some surfaces to give the crystals their unique appearance, so don't immerse your crystal jewelry in water. That can damage the surface of the crystals. Never use an ultrasonic, ionic or steam cleaner to clean your crystal jewelry. And never use a toothbrush to clean crystal jewelry. That will easily scratch the delicate coating. Always handle crystal jewelry carefully to avoid scratching or dulling the crystals' finish.
The sharp edges of the holes in crystals will cut though silk thread so wire or non-breakable nylon is the usual stringing material. Those materials will not be damaged as much as silk thread would be if they get wet. It's still best, though, to never soak your crystal jewelry in water. Instead, wipe lightly with a cotton cloth or cotton swab dampened with diluted window cleaner to brighten up your crystal jewelry again. If your crystal jewelry is properly stored between wearings, intensive cleaning may never be needed.