The first and foremost thing that you need to check is your passport. Has everyone that is travelling got a valid passport that is in date and has space to be stamped? Even babies now need a passport, and obtaining one usually takes up to 6 weeks, so this will need to be applied for in advance.
Luggage is often another worry for many passengers when preparing to travel. All airlines will have luggage restrictions on weight and what you can carry in your suitcase and what should and shouldn’t be in your hand luggage. If you get this wrong, you may have items taken away from you or even find yourself in trouble with customs.