Always use a lens hood unless you are somewhere so tight you can't manouver the camera with it on. If you don't have them cheap copies are readily available on ebay for most lenses.
Make some attempt to calibrate your monitor - the Photo Friday calibration is free and will help with black and white points:
Photo Friday: Monitor Calibration Tool
And if the histogram on both camera and PC is short at the dark end, consider dialling in 1/3 or 1/2 EV underexposure all the time, except of course for snow, white sand and similar shots.
PS can you post an example? With the EXIF?
PPS what exposure mode are you using?