UL procedure of PCB Design
While I'm by no means a UL expert, I can say this:

1) You don't need to use UL listed components to have a UL listed design, UL listing is something you get by having a finished product that passes the appropriate UL tests.

2) Yes definitely follow the appropriate creepage and clearance distances for the voltages your product is likely to encounter (using bigger clearances won't hurt at all and if you can't accommodate the clearance for any reason, board cutouts or conformal coatings can often work just as well - speak to your local UL lab)

3) I don't think there's anything special about PCBs that go into UL products other than using the right clearances and creepages (and getting a conformal coat if there's any possibility of moisture ingress)

4) the UL lab will want a finished (working) product, unless you want to get each section individually certified (which is not worth it for a product that will only be used in it's finished state). Sending them a bare board won't get you anywhere.

5) They will require at least some information on how your product will be used and what it does and the environments it will have to work in, they can most likely advise you on which tests are applicable, they won't just take your money and do some arbitrary test, they are a safety agency, if you ask for advise they have a duty to give you assistance (even if you haven't paid them yet)

6) Speak to your local UL lab, they should (and likely will) be able to give you advice on things like relevant requirements, things to avoid, that sort of thing, they have knowledge and they will likely be happy to share it.

7) Unless there is a specific need to use nonstandard materials in your PCB, I don't see much of a need to have much interaction with the PCB manufacturer, good ol' FR4 is found in thousands of UL parts (laptops, chargers, phones are almost always UL listed). The only time I'd imagine you'd need to speak to the PCB manufacturer is if you need cutout slots or conformal coating (and they can probably work out the cutouts from the cutout lines your PCB outline drawing anyway)