Keep them gunk-free. Cosmetics, sunblock, perfume and hairspray can dramatically dull the lustre, as can your body oils and perspiration.
Chemicals such as bleach, sulphur and detergents can also erode the gems, leaving them dull.
I quality check every single pearl, making sure that the lustre, shape, size and colour are perfect for you. No two pearls are the same, so you can be assured that your pearl is completely unique, just like you.