Re: Fuel Logs
Your fuel-required calculation should include: fuel for the start, fuel for the trip, a percentage extra (e.g. 10%), plus a reserve (e.g. 20 minutes flying time). Other than the start and trip fuel, the extras may be down to you or your employer. There may be more, e.g. holding fuel, but let's keep things as simple as possible.
If you subtract the start and trip fuels from the total, you end up with the fuel remaining on landing, provided, of course, the trip goes according to plan.
When you do a fuel check in flight, calculate how much more you expect burn off before destination, subtract that from the fuel remaining, and it should not be less than the calculated landing fuel. It should actually be that figure plus the 10% of trip fuel.
The reserve fuel figure (20 minutes in my example) should be constant, and imprinted on your brain.
Part of the fuel checks should include a calculation of fuel used since the last check, and compare it with the expected consumption rate.
Personally, I do a fuel check every 15 minutes.