It isn’t a true vector program like Illustrator or Inkscape, but you can achieve the same look and (mostly) the same scalability in The GIMP. So, this isn’t true vector. The same look associated with vector can be achieved though–only sometimes in greater detail because it’s a raster program.
Tools we will be using: Pen tool and Bucket. I will try explaining the pen tool in a later tutorial, I’ve always failed at explaining it though IMO. =X
At the time of this writing, I am tracing an anime scan from Card Captor Sakura, purely for practice sake. It’s my second “vector”, so yes I am a newbie and you may disregard anything you see here if you feel need be. However, I’m a quick learner and feel I have a very good grasp of what I’m doing. Even developing my own techniques so far. =)
Select a color suitable for the outlines of whatever area you are going to trace. In this case, CLAMP typically has thick black lines, so I decided to use the same look–I’m using a dark brown, close to black, color for outlining her hair. Using the pen tool, outline chunks of her hair (numbered 1 - 4 in the order I did it):
In your tool options dock, push Create selection from path, you should now see marching lines where you outlined. Inside the selection, fill it with your desired color with the bucket.
Repeat this same process for all outlines. The alternative method that works well for small or more evenly shaped lines is to make a single path with the pen tool, then instead push Stroke path.