You can use Guassian Blur to reduce noise or buy one of the commerical suites like Noise Ninja
I find it is best to do all editing as a layer, so each filter, edit, etc is applied as seperate layer.
and when merging the layers, I usually change the opacity of the layer, so filters naturally mix into the image.
One of the best ways to do levels, is when you have the levels dialog open,
is to hold down the ALT key while moving the white and black point.
When you hold down the ALT key on the black point, the image will turn totally white and as you move the slider, you should start to see coloured pixels, as soon as you seen pixels, this means the levels are correct. The same happens with the white point slider, although the colours are reversed. This is supposedly the mathematical way to do it
Regards
Darragh
  