hey zahra,
well i do edit my pics in photoshop, i just play with the curves, levels, and brightness/contrast but i very rarly change the actual color of the picture. Sometime i reframe when needed...
here is a before and after photoshop for you (this one is the most extreem modifications i made to a pic)

i have been studying computer graphics in paris for two years now and we did a lot of artwork last year. We never had photography there, it's just an other hobbie of mine, but the little artistic background i have now really helps, I actualy think now when i take pictures (never too much though!)
well i hope i replied to all your questions...