What I would find in your bag

One or more of the following:

1. Notepads + Pens
2. Drink, normally about 600ml of Coke or Bottled Water
3. Hat or Mini umbrella for minimal weather protection
4. Laptop/Mouse/Charger - The Laptop is a heavy, SLI'ed beast so I only take it with me when I need to
5. Glasses case - Though normally only if I'm going to see a Powerpoint presentation. I rarely need them otherwise.