Great topics Edge and Pugwash!
I also find it helpful to check the levels and move the arrows in to the edges of the histogram.... hard to explain without the pics, how do you take screenshots?
Then theres healing tools to remove dust, selecting dial for seperate contrast, colour balance if your camera cant set white balance..... etc etc
Some of these programmes can be a daunting at first but just muck about on them after all its digital (free)so take lots of pics and have a go at manipulating them... you maybe surprised at the results.