This is still a beginners guide for the simple fact that I'm a beginner, but thanks to some very good plugins it's a breeze (even for me).
Step 1: Things you need
Paint.Net of course
For the plugins I've downloaded 2 packs
Ed Harvey Effects
(or download below)
These give you lots of effects to play with ;-)
We're going to use, besides the standard tools available to us,
Color Tint (Ed Harvey Effects)
Extract Channel (Ed Harvey Effects)
Color Balance (BoltBait's Pack), this one's under the Adjustments menu instead of the Effects menu.
And most important, a photo you need or want to edit.
No I didn't fly all the way to China to take a nice photo. I found this photo on openphoto.net, it's free to use under the Creative Commons Attribution-ShareAlike license, so perfect for this instructable.