Gradient Map tips (don't forget to play)

As some of you commented you were going to try gradient maps, just some tips:
- remember to use it with moderation (it can be as bad as too much alcohol)
- play with the colors and opacity to achieve different effects
- you can use a mask on the gradient to soften it in specific areas
- be careful when you use greens on people skin (they get a zombie-look). On the other hand cold colors can be great for landscapes.
- it can be used to unify color palettes (if you have used more colors than you wanted)
- you can use it on photographs too (the result can be a little instagram-ish)