Welcome to Part 1 of my basic editng tutorial. We will mainly look at colour changing and some other tools. In Part 2 we will discuss filters in detail and how to use them. 
Before we start, you will need to know how to capture and save a screenshot in flight sim. If you don't know how, click here.
I am using Adobe Photoshop Creative Suite 2 to edit, all other Photoshop users will know where to locate named tools, etc, but i will give instructions for Creative Suite 2.
If you don't have Photoshop, i suggest downloading a FREEWARE program called GIMP.
Also, this is my way of editing and what i do is how i wish to do it, I know I'm not the best at editing but I created this in an attempt to help others who share a passion for aviation. Please don't criticize me if I appear to be doing something wrong.
Start
For this tutorial I'll be using the following image - you will want to download it and use it as well so you can follow me step by step the first time. 
First step, open up your image in your editing program.

At this point your image will be very large, so we need to resize, try 800x600 pixels. To do this select Image -> Image size, and enter 800 for the width and 600 for the height, making sure the units of measure are pixels.
After this process is complete you may notice that the image looks a bit soft; what I tend to do next is sharpen the edges. To do this i use a sharpen filter. Filter -> Sharpen -> Sharpen Edges. This will make the image look much more crisp.

Now we want to really start editing. Before i go about changing the colours, levels and contrast I usually do any jobs that require filters, but we'll skip that for the purposes of this tutorial (stay tuned for Part 2 if this interests you).
A great tool which i use is Auto Colour - this will usually enhance the images colours, but can sometimes spoil it if used on a night shot. So here im going to give you 3 steps:
1. Auto Colour; Image -> Adjustments -> Auto Colour
2. Auto Levels; Image -> Adjustments -> Auto Levels
3. Colour Balance; Image -> Adjustments -> Colour Balance, and add red, usually use around +20 to +30.

Now your shot should look noticably different from what it was when you started. The next thing that i would advise is playing around with the shadows and highlights. This is what i do:
1. Reduce Shadows to 0.
2. Increase highlights to between 10 and 20.
Try it and see if you like the look of it:
Image -> Adjustments -> Shadow/Highlight...
Next I normally add the photo filter. To do this:
Image -> Adjustments -> Photo Filter...
Select Warming Filter (85) and set the density to around 15%.
We're getting there!

Now, go back to Image -> Adjustments and select Brightness/Contrast...
Don't touch the brightness slider but adjust the contrast to +*, i normally go around 10 but it depends on the shot, you decide.
Now the shot looks a bit like this:

Only 2 things left to do!
In your pallet, select the two colours to a bright white:

And now go to Filter -> Distort -> Diffuse Glow...
Use the following settings or something close:

And finally, select the blur tool from the box at the left hand side:

Use the settings shown inside the blue ring.
When finished, zoom right up close to the plane and blur the edges of the plane to hide any jaggies, do it for the whole aircraft.
Now you are done! And should have an image like this...

I hope you liked this small tutorial and that it is to your benefit. Please post your final outcome as it will be interesting to see what you guys can do, or need more help with.
Part 2 will show more use of filters and will be up as soon as I can get to it.

Enjoy and have Fun!
Tom.
