When you arrive at the security checkpoint you should have:
Removed all outerclothing and headgear.
Removed belts and large metal jewellery.
Emptied your pockets of loose items such as coins.
Taken out your 1 litre bag with liquids, larger electronics and your mobile phone so as to put them separatly in a tray on the belt.
If you get ready before you reach the security checkpoint, screening will go more smoothly.
Find more information here.