I have really bad melasma from the pill and hormones + sun exposure (and have never been pregnant) use the new facial sunscreen by neutrogena SPF100 - my dermatologist urged me to use this and it does help. I slather it on my face, neck every single day before applying makeup. He gave me samples of Tri luma so I could try before I spent money. He insists that it works but at $200 a tube, I'm reluctant...I also read that as soon as you stop using it, the spots can/will come back with a darker or grayer appearance. I use another product with hydroquoinine (sp?) and vitamin C and it helps a little....but the biggest thing as the other person said -- is avoid the sun as much as possible (hats, 100 spf, shade, etc) I love the outdoors and beaches, but as long as I wear my SPF100 liberally and faithfullyb I can control it. I have never successfully gotten rid of it but I can keep it to a minimum. I would LOVE to get that laser treatment which removes it, but it's way too expensive for me and painful I hear.
I recently tried Covergirl/Olay simply ageless products---the corrector for dark eye circles works on the melasma like you wouldn't believe!! I can almost completely hide it with this!!! Worth a try if you also want to conceal it.