Hi
As far as I understand it, in a three phase sharpening workflow (which may also include separate edge contrast enhancement) the capture sharpening, (sometimes called de-fogging) is about overcoming the slight softening effect of the anti-aliasing filter fitted over the sensor, especially if the camera was set to No in-camera sharpening. It seems to be common practice to do this fairly early on in the processing workflow now days, before attacking curves, levels etc.
It isn't really about making soft images due to focus, lens or other technical issues sharp, although it may help a bit.
Further sharpness can be added by applying local sharpening and also apparent, or "relative" sharpening by applying softening / blurring effects in order to enhance the sharpened zone.
That is effectively all I do to a master image, sharpening wise.
The final phase, and often the most dramatic is the output sharpening, and that is when on a file that is destined to be printed things can start to look a bit ugly on the screen. With practice and review, the relationship between screen and print will develop and judging it will become easier.
Try experimenting by making a print (or a small crop from a print) and keep sharpening and printing until you push the sharpening too far. See if these setting vary from paper to paper and type of print to another.
Getting things to look sharp for the web has equal challenges too, but at least one has a reasonable view of what is going on, at least on you own screen anyway!
