I guess I thought I had read this thread, but, surprise, here is a wealth of info! I have some thoughts...
First, if your photo is for the purpose of selling, you want it to look as close as possible to the real thing so that your customer will not be disappointed and return the item. You want it to look good, but not too good. The very best thing to do in this case is to include multiple photos in different light. You have no control over the light when the customer first opens the box, so having more than one lighting example will prepare them for what they first see.
I would especially caution against using water in photos of pearls you are selling without disclosing the fact. But, when you just can't get them to look their best, the water trick is a great shortcut.
Here, I spent a couple of hours trying to capture the color and finally resorted to water. I used a fine sable brush to painstakingly remove the bubbles - and there were a zillion tiny ones that only showed when the photo was on the computer. Extra strong reading glasses are handy for this!
Focus is a big issue. I have a super duper SLR Nikon and a little Nikon Coolpix. The depth of field difference means that I get better consumer photos with the smaller camera because more of the field is in focus at the same time. That means that more of the pearls look sharp and shiny.
But, if you have a ring or earrings where just a small part needs to be sharp, you can do a soft focus background with the item glistening in the foreground - very arty!
I only use Photoshop or Elements to do two things. First, to correct the background color - very very handy. Click on the area that should be white and woo hoo it's fixed. And who hasn't got a fabulous photo and then seen a little cat hair or bit of dust? You can just smudge/erase it out.
As for light, I have all the fancy white box/reflectors/studio lights. You just have to continually experiment. Sometimes I add a high intensity lamp to spotlight because the white box can take away too much of the shine.
Best of all is indirect daylight indoors, near a window, or in a sunny room. Try putting yourself between the window and the pearls - that can sometimes make them pop the color.
I hope everyone is having a terrific weekend,
Blaire