This is the basic way to clean manga for coloring
(please dont bash this page, the bandwidth is limited.. "backup" is for when imageshack goes down only")
First, open a "shannaro" scan (shannaro's lines are better)
Next, select the "magic wand tool" on the left panel.
Hover over the area you want to select, and click.
Now, go to Select > Modify > Contract (this will contract the selected area by "x" pixels)
This screen should appear. Depending on how thick you want it, insert a number of pixels you want to contract it by.
(1 for thin, detailed lines) (2 for regualar use)
The selected area should have contracted a bit, now you can delete.
(Notice how there is a black border left.. this is for us, Zarosaki, to color )