Packaging accounts for almost half of what ends up in the landfill, so look over the daily leftovers that you are normally tossing in the trash and see if you can put any of them to good use in other ways.
Focus only on the materials that you have a vision for and that you or someone you know could actually use in future projects. You don't want to keep things just for the sake of saving, or you'll end up with a lot of unwanted clutter.
Some of the more versatile things to save are:wine corks
mesh fruit bags
small glass jars
plastic bottle lids
small tin packaging
rubber bands off produce