Here are the things I do:
I use my own cloth grocery bags.
I buy whole foods, rather than processed. That means cooking from scratch, rather than eating something pre-made, in a box, in a plastic, microwave tray. Whole foods have less packaging than processed foods, and there's less waste.
I compost my organic waste from the kitchen. Anything cut off vegetables, or anything that goes bad goes to the compost bin. I like to snack on peanuts, so peanut shells go in the bin, too.
I wear my clothes until they're worn, or holey, or stained with paint (occupational hazard). Then I turn them into cleaning cloths, and use them until they fall apart.
I use old t-shirts in my Swiffer, shake them out outside, and then throw them in the wash to reuse, rather than buying disposable refills.
And mostly, I don't buy stuff I don't need.