The biggest thing you can do is probably to just buy as little stuff as you can. There is a lot of packaging waste in the supply chain before you even see the product, and even if it's recycled there's still a lot more impact than not getting it in the first place. That means being willing to spend more up front on higher quality/more durable things.

Avoid fast food whenever you can. The packaging they give it to you in is only the tip of the iceberg of reasons not to support it. Life's too short to eat bad food.

I never thought of it, but I wonder if you go to a real food restaurant and have food left over if they would be OK with you bringing in your own reusable leftover container rather than giving you a throw away one? I eat out socially and I'm getting a little better at not eating the whole enormous portion just because they put it in front of me, but that does mean taking home a frequently leaky takeout container.