First u will need Photoshop: http://www.mediafire.com/?12li2kfo7x5iu
I'll use part of ur picture for this tutorial
In this tutorial we'll use lots of Polygonal Lasso Tools
Lock transparency is a very good feature allow u to lock the transparent part of the layer, so that u can edit the un-transparent part without touching the transparent one.
The layers below another will be put "under". I think u get the picture.
To zoom in press ctrl + space, zoom out use ctrl + alt + space, use spacebar to move the canvas.
OK before the tutorial, I must say first that this is a noob way, I don't know if there are any other ways for this but... I'll tell u wat I know
if u have only one layer and it's named "background", then right click on the layer and choose "layer from background". Name it "line".
then use Ctrl + Alt + Shift + N to create another layer, use the paint bucket tool (G) to make it white and put it under the layer "line".
Now I want u to select the polygonal lasso tools, if u can't find it, right click and hold the lasso icon on the toolbar, they will let u choose the polygonal lasso tool.
This will let u click and select the "points" for ur selection. Make sure u're selecting the "line" layer. Trace along ur lines and select a region which doesn't have any lines. And delete it.
Remember, don't cut the lines. When u're done, it should be like this
Now it's time for the transparency lock comes to play, lock the "line" layer and use the brush tool (B), color black to make all the lines black.
And it's done, cleaning finish
Hope u understand, I'm not quite good at giving instruction...
I'll do one for screentone shortly...