I have read two differing ideas when it comes to cropping your images during post processing.
1. Crop first, that way you are not editing stuff that isnt going to be in your final image anyway, why waste time editing something that is getting the chop?
2. Crop last, do all your editing and then crop, cause once you have your final image, you will know exactly where you want to crop it.
I tend to fit into category 1 above, where in your post processing , do you crop your image?