Well, I know what it feels like to not have a clue what you're doing with an image manipulation program (Photoshop, GIMP etc.), and I know this is the first place I came lfor help when this feeling set in. Because of this, I decided to (try) and make a thread containing all your little tips and tricks that people may not know about your preferred image manipulation program. These can be anything, and can be as long (full step by step guides) or short (quick tips) as you decided you want them to be.
This could be a really useful library of knowledge if it gets working, so i hope it does =D
Ok, i'll post the first tip:

When cleaning, if using a flatscreen monitor, tilt it backwards and you can see where all the smallest colour differences are on your image. This makes it easier to get a perfect image, and takes a considerably smaller amount of time.
Now, most people used to programs will be used to this, but newbies won't so... yeah, thats also good example =]