Yeah, there are stacks of posts on this. However, amongst other things:
- get your certificates in order, ideally completed and in a file
- have all of your test kit ready including lockout kit, proving unit (ideally), meter(s), etc
- have your insurance certificates to hand
- choose 2 decent installation examples
- rehearse some tests at each location and research what the correct results for each test should be.....know which books to use to check
You should have had a leaflet from the NIC stating what you'll need to have ready?
Incidentally, it seems that the inspectors vary quite a bit so there doesn't seem to be any hard and fast rules as to what they'll check. If it's your first inspection get the basics done properly including safe isolation procedure!