If the checklist is interrupted always start again at the beginning, or Mr. Murphy will ensure that you start one item below where you stopped - which might be you miss the fuel selector !
Done that, didn't do the whole check list "just to taxi to the fuel pumps", and then skipped "the bits I'd already done" when starting up again.
But whoever wrote the club check list had thought of that one ... there was FUEL BOTH for a
third time in the just-before-take-off checks, at which point I spotted it.