Cleaning a scan basically means making the scans look good.
There are many steps in the process of cleaning a scan:
1. Colour-settings: Make sure the scan is in greyscale mode or, for colour images, RGB mode. [+] [-]
2. Rotating: Rotate the scan to have it aligned correctly. [+] [-]
3. Merging: Connecting two pages that are part of a double page spread. [+] [-]
4. Cropping: Crop out unneccessary parts of the scan. [+] [-]
5. Leveling and dusting: Level the image so the blacks are black and the whites are white without damaging the greys then clean any specks that were left. [+] [-]
6. Redrawing: Complete any necessary redrawing, e.g. restoring the background behind offtexts. [+] [-]
7. Resizing: Resize your image to have a web-compatible size (depending on your group this may not be wanted) [+] [-]
8. Cleaning bubbles: Clear the text from the bubbles. [+] [-] [Action]
9. Saving: Save the image. [+] [-]
Other useful stuff pt.1: Adjustment layers. [+] [-]
A useful alternative to the usual leveling is to use adjustment layers. Adjustment layers are basically specific layers that change the look of all layers below when switched on. By using this, the original page stays completely intact which makes them extremely useful; especcially if you are not sure about your leveling.
To use adjustment layers click the half white, half black circle in the layers dialogue and select the option you want to use (usually the leveling option). Then level like you usually do:
Now you will be able to see the adjustment layer in the layers dialogue.
There are some interresting things about adjustment layers; the most important being that you cannot edit them normally. The burn/dodge tool (O) does not work at all on adjustmentlayers. You need to use those tools on the given layer below, usually the background layer. If you want to use the brush tool (B) do dedust, make a new layer (Control+Shift+N) on top of the adjustment layer, since the brush tool disables the adjustment layer in the given area. If you do not do so, this will happen:
Other useful stuff pt.2: Training Raws. [Low Quality]