I'd also like to add a tip regarding feeding cable through difficult runs (e.g. in the ceiling or through the bilge space). Once you've fed something through to find the route, pull a piece of strong synthetic cord (so it won't rot) through. Then use that to pull your cable(s) through, and at the same time include another length of cord. Leave this cord in place, with the ends tied off so they don't get lost. Then when you want to thread another cable (almost inevitably!) you've got the cord there ready to use.
And of course if you do use that cord, pull another one through to replace it!
Rick Jones (Treasurer) 1994 Mac 19 "White Lightning", Isle of Wight