Secure with parcel tape top and bottom and never just fold the flaps over.
Mark with felt tip on the top of the box or on the tape itself as to the room it is going to and also mark clearly if it contains fragile items.
Don’t make boxes too heavy, it is often a good idea to have heavy items at the bottom and then fill with lighter or softer goods.
Ensure bottle lids are all tight and pack standing up.
Any knives or sharp items should be wrapped prior to packing to ensure they cannot protrude from the box and cause injury.
Last important tip… get a good nights sleep the night before the move with the peace of mind that comes from booking the right company for your move.