If you're like me, sometimes what comes out of your camera and onto your monitor isn't quite what you had in mind when you took the photo. Sometimes the image might look a bit flat or dull, despite playing with curves or levels in Photoshop.
Have you ever tried the blending modes? They can really add something dynamic to an image. So where do you find blending modes? When you open an image in Photoshop, you'll automatically have a background layer in the Layers palette. You won't see the blending modes until you add another layer - this might be duplicating your background by pressing Ctrl J on your keyboard, or you can add another layer with color or a gradient in it, for example.
Once you have at least two layers, the blending modes will be accessible - look directly under the Layers tab, and you'll see a drop down box with Normal in it. Click on that tiny arrow...there are many variations including Multiply, Overlay, Screen, Color Burn, Luminosity, Darken, Lighten, Hard Light, Soft Light, Linear Burn...and they all give your image a unique effect.
Most of the time, I will use blending modes in conjunction with a mask...so I attach a mask to the duplicate layer, and then I can selectively paint away on the mask to reveal the layer beneath where I really DON'T want the effect to appear.
Multiply, Overlay, Color and Linear Burn and Hard Light will darken your layer...as will some of the other effects. This is handy when you want to bring attention to your subject matter and less focus on the background - see the lamingtons as an example.
This image didn't look like this straight out of the camera...I darkened the edges selectively which tends to draw the viewer's eye directly to the subject (our eyes are naturally drawn to the lightest parts of an image.)
You can also use a gradient fill, with two colors, and then one of the blending modes to achieve something like this beach scene on the left. Remember you can always reduce the opacity of the layer if it looks a bit too strong. The original shot had very dark lighting, it was sort of purple and grey...not the best for stock. With a gradient overlay, it made a tremendous difference!
If you need to know more about how layers and blending works, don't forget that Google is your friend - there are lots and lots of tutorials online that will show you everything you need to get started. Good luck and happy experimenting! :)