Check out Ecobricks.org or visit the Facebook group.
Refuse (to bring it in, to use it etc) so carry your own cutlery and cup and straw.
Reduce the amount you use- (sounds so simple but it's hard work, but for example find a grocer that's plastic free so you don't have to buy everything wrapped in plastic)
Reuse any plastic you do accumulate
Rot /compost any degradable waste
Recycle- check the labels, learn what your local authority does recycle, wash it all, don't contaminate etc.
I got a big bag in the kitchen and filled it with all our non recycleable plastic for a week. It was shocking. Horrifying. Then we've just as a family tried to make small changes. So we've switched brands on lots of things, we've switched supermarket (to a grocer + Lidl), we've stopped using cling film, I've made a 'kit' which we take everywhere with reusable cups, cutlery, etc and bags,
We've changed our coffee and our cat food.
All these take time, and I won't lie, take ages and sometimes cost more money. But it's so important to me that I'm prepared to do it.
Our first ecobrick took two days to fill, our 5th (current one) has taken 2 weeks, and our landfill bin went out with just one bag in it this fortnight. I see that as a tremendous improvement in just 2 months.