Two of the easiest places to switch to reusable items are in the kitchen and on shopping trips.
Reusable grocery bags are the base level. If you do nothing else, do this.
I made rags out of t-shirts I'd cut up for other purposes.
I picked up cloth napkins from yard sales.
Then reusable produce bags and cloth bags for produce or bulk foods. I'm actually known at my farmers' market for bringing my own produce bags all the time - almost everyone else uses plastic ones (!!!)
these from Flip & Tumble. You could also make your own if you're savvy like that - my Grandma made my cloth ones out of her quilting scraps. The rice bag came from a friend - I told him about my shopping habits, and he said he'd bought rice in this cloth(ish) bag, but wasn't going to reuse it. So now it's mine!
Finally, I fill glass jars with dry goods instead of buying pre-packaged foods and spices.