What I'll do is run through a simple work-flow in Photoshop Elements, but the techniques work just as well in the full Photoshop, Gimp, or any other layers based software.
Sunrise, by Shade.
First up, I'd like to say that without further editing I like this photograph well enough. There's nice colour in the sky, foreground interest and you can see the morning mist down in the valley.
But you know me, I like to dive in and change things from the original, trying to re-create perhaps the feeling you would have had if you had been there watching this beautiful scene unfold.
What Could We Have Done Differently At The Time Of Capture?
Right, well Shade shot in Aperture Priority Mode, F13.6 for 1/3 second at ISO 64, with a nudge of exposure compensation to slightly underexpose the shot.
These were good choices, giving a large depth of field. Hopefully he used a tripod or some sort of camera support, and I'd be tempted to try a larger Aperture next time, say 6.8 or 6.3 to see if that might make the image sharper. I know that sounds wrong, but often lenses are not at their sharpest when stopped all the way closed (or open).
What we could do next time is play around with the exposure. In "extreme" situations - Sunrise, Sunset, snow, beach shots, light subjects on dark backgrounds and vice versa, any cameras auto-exposure settings get fooled. Quite simply digital cameras like to work out exposure on averages, what a normal scene looks like. So if scene is far from average, like those mentioned, we need to make allowances for it.
First up we can just set our cameras to "sunset" scene position mode. That's fine, but we want to learn more, so we can use exposure compensation instead.
With exposure compensation (normally the little + and - button) you're telling the camera to darken or lighten the scene relative to what the camera thinks is the correct exposure.
We know that in the evening or early morning the light will be lower, so our cameras (if in any of the Automatic Exposure Modes - Auto, Program, Shutter / Aperture Priority) will try and make the scene lighter, over-exposing the image, de-saturating colours and losing detail.
To get around this for Sunrises / Sunsets, dial in under-exposure with Exposure Compensation. Experiment, nudging down the settings and taking shots until you can't get any further. Review the shots and you'll be amazed at how the colours will come to life.
If the camera is really fooled, Exposure Compensation won't give you enough elbow room, so you'll have to switch to manual mode and deliberately underexpose.
The other control would be white-balance. To be honest when shooting out-doors, I'd leave my camera in auto, but you could change it to a custom setting and take a test shot of a piece of white paper. You'll find that under-exposing will make a bigger difference.
A Note On Photo Editing
When using any photo-editing software there are many ways of doing the same or similar things to our photographs - so you may look at my methods and achieve the same things in a different (and probably better!) way.
Also, never work on original files. We don't want to corrupt and lose them, but also remember that .jpg is a lossy format, every time we open, edit, and save we lose detail and quality, so we want to copy the photo, work on the copy, and save it as a TIFF or PSD until we're ready to output to .jpg.
First Step, Sunset Method: Layers Blend Modes
Open up your editing software, load up your photograph, duplicate the original layer (to keep it safe and for reference) then add a levels adjustment layer. (It can be another duplicate layer, or a curves or hue / sat adj layer, I use a levels adjustment layer rather than a duplicate layer because in early versions of Elements this in the only was to easily have a layer mask, which we'll be using in later methods.)
You don't need to make any adjustment to the levels, just press OK, but you do need to change the blend mode of the levels adjustment layer to "Multiply". Adjust the Opacity of that layer to fade the effect:
Sunrise Enhanced With A Multiply Blend Mode
Play around with the different blend modes for the top adjustment layer. Try colour burn, screen, overlay, and all the others to see the change they make to our image. Pretty cool or what!
To make the effect even more extreme, duplicate the adjustment layer, or just create another one, and see what that does. The scene will become darker, but the colours will become even more vivid.
We could just stop there if we wanted. If you want to go further, try the next step.
Second Step, Sunset Method: Using Masks And Painting With Light
What we did above made the sky look better, but we've lost the foreground. Remember when I talked about layer masks earlier? Now they'll come into their own - we're going to "paint with light".
Click on the layer mask, the little white box, to make sure its selected. Select your paint brush tool, make sure it's a medium-ish soft edged brush, in white, then start painting (on the photo) on the bottom of the image:
If you make a mistake and start painting over the sky, switch your colour to white and paint over to correct it.
So what's going on here? Well, by painting Black on the mask, we're hiding the effect of the multiply blend layer, allowing the brighter original to show through.
Sunrise With Foreground Masked
So, hopefully you've got an idea about blend modes and masks, and how you can use them to give your photos more punch. What you could do now is experiment - double click on the levels layer and adjust the settings to see how that changes your picture.
Why not add another levels adjustment layer, but this time mask out the sky, then adjust the levels layer to increase contrast in the ground.
Maybe finish off with a crop - perhaps a long and thin, pano type look?