A Cessna or Piper wheelplane on the ramp is pretty straight forward
A 182 ain't. Big ladders out for that one.
I've always found estimating the fuel burn a useful exercise. I can get it down to a litre or so error an hour on the stuff I fly. Just fill say a 28 to tabs, do a flight out somewhere an hour or so away and come back. Say to your mate 'We have used x litres of fuel' and fill it back up to tabs. Then either look smug or stupid; you soon start getting it right.