Whatever is most convenient for you!
When you drop off materials at a nearby listing, if the container/bag/vessel you bring the items in is NOT on the accepted items list, you will be asked to take it back home with you.
Things like plastic bags and plastic tote bins are typically not accepted, but are perfectly acceptable to transport your materials in. Just ask for the bag/bin back after the items are unloaded and the host will be happy to return it.
Overall, we want to limit the amount of "trash" that is created. The more we can keep the items strictly to what is on the accepted items list, the more earnings our community can get and the less hassle it is for the host.