Know what you are doing:
Noise
Basic pre-processing:
Bias, Dark and Flat
Advanced pre-processing:
Superflats and sky background
Fringing
Image weighting
Putting it together:
Astrometry and photometry
Image coaddition
Never underestimate:
The importance of dithering
Looking for photoshop science?
Making pretty colour pictures is not the same as data reduction.
You are probably looking for some image processing tips.