I'm using Photoshop and I use the sharpening method suggested in the editing guide on this site - with three successive passes on separate layers of 50, 0.3, 0 and then rub out any areas which have ended up too sharp. I have a reasonable record on oversharp/soft rejections (helped by a few appeals recently!!) so it must be a fairly reliable method.
The other thing you need to be careful of is how much sharpening the camera itself is applying before you even start editing, even if you are starting from the RAW file. My Canon produces RAW files in a range of 'picture styles' which have different levels of sharpness and other adjustments already made, and it pays to either use a 'neutral' picture style or to reduce the amount of sharpening using the slider control in the RAW plug-in before you then start applying USM
yourself. If you are editing from jpegs, then you don't have the options of doing this and it is easy to then end up with an oversharp photo even if you haven't applied much sharpening yourself.
Hope that helps.