Get the right travel insurance. Check whether your medical insurance covers international travel. if not, it is wise to have a travel insurance.
Travel insurance covers against personal, baggage and cancellations.
Make sure you do not exceed the baggage allowance.
Arrive ta least two hours before the departure to allow enough time for check-in, Customs and immigration, etc..
Know the exact time difference between your city and the place you are travelling to.
Have copies of your passport and other travel documents.
Always have a (digital) back up of your important travel documents.
Carry sufficient amount of local cash.
Have a charger adapter. Some countries have different size plugs.