Do not leave your bag unattended in a pub or café.
Do not leave your bag hanging on the back of chairs, use bag hooks that hide the bag under the table.
Make a point of asking your friends to look after your bag if you are leaving it.
If you have a bag avoid sitting close to exit doors or toilets as these offer some cover for thieves to go to following a theft.
If you are going out for the evening leave your laptop at the office where it will be safer.