How do I know where to clip the nail?

You should clip the nail a little way in front of the quick - in clear nailed piggies you can see this as a pink blood vessel in the nail - in darker (black) nailed pigs it can be harder to know where the quick is- some people shine a torch under the nail to show the quick, this will show up slightly darker than the nail, you can also normally see an indented line under the dead bit of nail which can also look a bit lighter/drier. You should safely be able to clip this part off - it is really experience - if you are not sure where the quick is err on the side of caution - you can always make an appointment with your vet / or ask a local breeder / rescue who will show you what to do.

That is an excellent diagram of a piggy nail. One option to clipping is using a
Dremmel Mototool with a sanding bit on it. That's what my vet uses, and rather than clipping the nail and risking clipping down too far, it sands the nail down so it's shorter and blunt. If you're wondering what else you can do with a Mototool, it's great for making and repairing acrylic fingernails, lol.

HAHAHAHA!!!!! I'll have to make a section for beauty tricks lol