I like minimizing trash before it hits the RV. For example, cereal goes into plastic containers, disposable bowls and such get unwrapped and stacked, shampoo goes into the dispenser in the bathroom, sugar, salt, etc. go into their appropriate containers. Then, I toss all the packaging away before I leave the store.
For trash in general, I try to use plastic shopping bags. The reason is that if I stopped at a gas station and tossed 1-2 of those in a trash receptacle, nobody would really care. If I tossed a full size 30 gallon garbage bag, it would get people complaining about abuse.