and always do a physical check, and fill right up if unsure
Yep, I was atught that you ALWAYS look in the tanks - even if the fuel bowser has just been and filled her up - get up there (Cessna's - obviously!) and have a check. It also helps to be the one responsible for screwing the cap on tight as well!
Now we have a dip stick, I record the fuel before every flight, and then after, and have worked out an average consumption - it's scary how different it was compared to what I was always told! This lead to ma landing with only 45 mins of fuel on one occassion - I know that is acceptable, but if Luton hadn't have cleared me through their zone, I would have had a longer detour...