One point that doesn’t seem to crack much of a mention here is what happens in-flight to update the fuel plan enroute.
Yes, the first critical step is to work out as accurate a plan on the ground as you can, but then you’ve got to do what you can to ensure it’s working (or not, and make decisions accordingly).
A couple of pinpoints per leg and a watch gives you a ground speed and a fuel flow (depending on the limitations of your your fuel indicating system, but better than blind trust), while any GPS can tell you the time to the next point but not to destination, if there’s a significant track change.
How many of us do these simple but critical calculations in whatever we fly?
If you’re diligent with your fuel management and still get short of fuel due to factors beyond your control, then you’re still way ahead of Joe Bloggs who jumps in and launches in blissful ignorance.
If you’ve done everything right and for some reason are into your fixed reserve, then declare a mayday, get priority and assistance and be bloody happy about it.
If you didn’t plan or check, well have a look in the hall of mirrors.