Maintaining vigilance while refueling so that the correct variety of fuel (usually 100LL: 100 octane low-lead) is used to refuel your aircraft is of the utmost importance to avoid engine failure during flight.
Careful fuel planning and fuel awareness are also important to avoid inadvertent fuel exhaustion.
>> Download free: All About Fuel
>> Download free: Aircraft Fuel Control
>> Download free: Time In Your Tanks
>> Download free: Aviation Fuels Technical Review (discussion on 100LL starts page 43)