Plan the legs with the wind triangle: wind correction, magnetic heading, groundspeed, time and fuel. When the plan is ready, check the ICAO flight plan format before you file it.
For non-commercial flights in a non-complex aeroplane (Part-NCO), plan to reach the destination and still land with the final reserve: 10 minutes for a local day VFR flight in sight of the aerodrome, 30 minutes for other day VFR, and 45 minutes at night or IFR, where IFR also needs fuel to the alternate. The rule also requires fuel for reasonably expected contingencies and delays (AMC1 NCO.OP.125).
The same items as the European flight plan form. Fields turn red when the format is wrong; the check list below says why and how to fix it.
Teaching tool. Formats follow ICAO Doc 4444 (FPL 2012) and EASA Part-NCO in simplified form. Always check the current AIP, your state's ATS office requirements and the aircraft flight manual. Example values are not for navigation.