Not having the necessary spare parts readily available.
Having to wait 3 months and paying exorbitant shipping fees to get spare parts.
your experience level
First time vs experienced.
More expensive models are easier to fly, but if you did not learn how to fly properly the results will only be a more expensive crash.
Buy a drone that suits your experience level.
Size of propeller
Drones with bigger propellers are more stable, but not as nippy.
Drones with smaller propellers are agile, but aggressive.
Is the drones battery built in or replaceable? If the battery is replaceable you can get more flying time. (Average flying time is between 6 and 10 minutes)
Having a universal battery connector can make finding spare batteries less of a hassle.
Larger mAh size batteries gives you longer flying time.
How susceptible is the drone to breakages. Open propellers and designs that has the propellers close to the ground.
Propeller protectors can solve one of the problems and can be removed later.
Landing gear makes take-off and landing less risky.
Ease of transport
Where you are going to fly the drone
Indoors vs Outdoors.
If your area is windy you would need a drone that has different flying rates. (Specifically a faster flying rate).
Heavier drones will be less susceptible wind interference.
After sale services
Place of purchase : Retailer vs Drone Specialist.
Buying a drone in a store you may often pay jacked up prices.
Drone specialist will also be able to give you better advice on buying a drone that suits your needs and be able to give you good after sale service when looking for spare parts or fixing or improving your drone.
Not all drones are ready to fly out of the box
Do it Yourself (DIY) vs Ready to fly (RTF)
DIY you still need to assemble or buy extra accessories for example some drones do not come with a controller. A separate one needs to be bought.