The method I use is sort of like HDR, but less complicated, so it will be easy to follow for newbies, but it still yields great results.
Be warned, this tutorial is written for new GIMP users, so if you just want to know what I did and how I did it skip to step 3 and yes, I know it's very simple so don't bother telling me I'm a n00b and this isn't good.
Edit: I did this all on one monitor and I realize that it may look too dark/bright on yours.
Step 1: Step 1: Download the GIMP and Install
and http://www.gimp.org/macintosh/ for mac. Just click the link that says Gimp on OSX
When it downloads, click the installer on your desktop and follow the onscreen instructions.
Note- this tutorial is done on a machine running windows Vista, and I don't know if the mac Gimp is the same, although it probably is.
Another Note- gimp 2.6.6. crashed for me a while after I installed it on startup every time. Before you become angry and spam me with hate mail go here http://www.gimpusers.com/news/2009-05-21/gimp-2-6-6-windows-problems.html and click download gimp 2.6.5., which hasn't given me any problems.
Step 2: Step 2: Fire Up the GIMP and Open Your Image
Step 3: Step 3: Editing the Photo
The first step in editing is to go to they layers tool box and click duplicate (pic 2) then select the new layer (background copy) and click: Colors>Brightness-Contrast and slide the contrast bar up to a point where the parts of the image that were black or darker in real life are the same in your picture. Below are my before and after pics, and you can see I chose a setting of +17 and used the trees as my guide. You may need to play with this for a while.
Step 4: Step 4: Editing the Photo, Cont.
To do this, make sure the dark layer is selected and change the layer properties. Click where it says "normal" and when the drop down menu appears, click "Darken Only" (pic 1)
Now change the opacity so that the light parts of the bottom image show through more. I set mine to 66%, but again the changes here are very subtle and may take a while to get right.
Image 3 is my picture so far.
Step 5: Step 5: Ramping Up the Saturation
First go to Colors>Hue-Saturation, and the box in pic 2 will come up.
From here your on your own, because each picture is different. You can see the before and after below.
Note: in the picture master is selected, and this means that it ups the saturation on all colors. After I set my saturation to 50, I selected the red channel and lowed it because the red made the leaves to pronounced. Then I also upped the green and blue independently, to make the leaves and the river very colorful.
This was my first instructable and I hoped everyone liked it, and ideally, gets some use of it. The colors in your picture don't have to be as pronounced as mine, which can be achieved by playing with the saturation, which brings up my main point:
THIS IS NOT A DEFINITIVE GUIDE ON HOW TO MAKE YOU PICTURES LOOK, BETTER, ONLY A SUGGESTION- EVERYONE'S TASTES ARE DIFFERENT.
Thanks for reading!
And now for some self-promotion- to see more pics like this, and other types of art go to my deviantART page at http://www.unit225.deviantart.com/