1.) Going to Pret or Eat to pick up a soup or salad to eat back at the office? Don't bother picking up a plastic spoon/fork, use the metal ones in the office! Extend that further, do you need the paper bag either?
2.) Try to forgo a straw if you can!
3.) The bristles on a toothbrush get splayed after you've used them for too long and won't clean your teeth properly, why not just give them a trim with your scissors and make them last another month! Afterwards, give them a wash and use them for cleaning the nooks and crannies in your house!
4.) Does everyone in your office have a bin each? Why is the necessary? So that you're working that 30 seconds longer instead of walking to a communal bin in the room? These bins get emptied once a day, one plastic bag a day for holding your one crisp packet and a banana skin! Ask for your bin to be removed, or share with colleagues so that you're all only using one plastic bag a day for your bin.
5.) Try to buy less of the ready made lunches from supermarkets and make your own. Save money too!
6.) Try to buy fruit and veg from your local market, instead of a supermarket where most of the fruit is wrapped in cellophane and foam holders
7.) Make your own cleaning spray
8.) Make your own washing detergent
9.) Make your own handwash
10.) Just buy less stuff, do you really need it? Is it just going to clutter your house and make it hard to tidy and clean? If so don't buy it!