Joe Crace provides a detailed introduction to custom nibs over at The Gentlemen Stationer. In addition to outlining various nib options, Crace also explains best practices for getting nib work done.
Of course, this process often involves a nib "grind," (i.e., changing the shape of the tipping material using a grinding stone, wheel, or a rotary tool) but it can also involve smoothing the nib on sandpaper and/or mylar sheets, increasing or decreasing ink flow to the writer's preference, resetting the nib and feed, or aligning the tines. When you walk away from an appointment with a nib technician, you should have a pen that writes perfectly for you and your writing style.