I've separated the planning into 3 groups. What do you think?
Departure
Weather (Current and Departure Forecast)
Time, Wind, Visibility, Sky, Temperature, Altimeter, Remarks
Navigation
Flight plan filed, Approaches, Departures, STARs, SIDs, TPA, Taxi plan
Airport
Runway lengths & slopes, Runway condition, Elevation, Radio frequencies, Airspace, Fuel, Food, Amenities, Fees, Frequencies, Obstacles
NOTAMs
Charts
Sectional, Terminal, Airport diagram
Aircraft
Weight & balance, Fuel on board, Landing distance, Take off distance, Performance, Fuel reserves
Equipment -- Radios, GPS, Auto pilot
Maintenance due -- annual, 100 hour, oil change, VOR check
Preflight
Safety
Passenger and crew -- Illness, Medication, Stress, Alcohol, Fatigue, Eating
Pilot experience, recency, physical condition, cancellation and alternative plans, personal equipment
Enroute
Weather (Current and Forecast)
Time, Wind, Visibility, Sky, Temperature, Altimeter, Winds aloft
Navigation
VOR frequencies, identifiers, altitudes, directions
NDB frequencies, identifiers,
RAIM availability
Distances, directions, altitudes, terrain
Special Use airspace - MOAs, Restricted, Controlled
Airways
Airport
Radio frequencies, Airspace, Fuel
NOTAMs
TFRs, PIREPs, jumpers, gliders, airshows,
Aircraft
Range, Performance
Destination including alternates
Weather (Current and Arrival Forecast)
Time, Wind, Visibility, Sky, Temperature, Altimeter, Remarks
Navigation
Approaches, Departures, STARs, SIDs, TPA, noise abatement, right pattern
Airport
Runway lengths & slopes, Airport diagrams, Elevation, Radio frequencies, Airspace, Fuel availability and price, Food, Amenities, Fees, photo from the air, Taxi plan
NOTAMs
Charts
Sectional, Terminal, Airport diagram
Aircraft
Weight & balance, Equipment, Maintenance due, Fuel on board, Landing distance, Take off distance