Used remask to separate the lemon and background, then used the level tool to make it "white"... Then made the lemon a little clearer, and flattened the image.
when you open it, hit Ctrl J, it will make a duplicate layer. Then on the bottom layer, hit Ctrl L, it will bring up your levels tool. Use the white eyedropper and select the white background.
Then on your top layer, separate your lemon from the white background... I use this plug in Topaz ReMask - Masking Made Easy
Then you can adjust the lemon separately, once done flatten the image by right clicking the bottom image and hitting flatten.
trial and error.. If you open the menus in PS, they have the shortcut listed right there... So after a decent amount of time playing with it, you start to pick it all up.