The regulations regarding the amount, weight and size of the allowed luggage depends on your airline and your ticket.
You should remove any old luggage labels from your suitcases at home. Tie together any belts and straps in your bags or backpacks to prevent them from getting stuck to the luggage conveyor belt. Lock the carry handles in place.
Attach name and address labels on the outside and inside of your suitcase. This will make it easier to find and identify your suitcase.
You can lock your suitcase if you so wish. However, security control employees may need to open your suitcase if they suspect it contains prohibited items or substances. In such a case, your suitcase may miss the flight if the lock cannot be opened with keys.
Do not leave your suitcase or other luggage unattended. If unattended luggage is detected, the airport security staff will take it over and deliver it to the authorities for investigation.
In order to increase passenger safety, remember also these general guidelines:
Packing your pushchair and pram
What goes into hand luggage and what goes into the cargo hold? What is prohibited on a flight?