Look in your recycling. What products are filling it up most? That's where you start.
To use myself as an example:
We go through a ton of milk, half my recycling seemed to be 4-pint packs (even when squashed). Started getting milk delivered in glass bottles which the milkman picks up and takes away. More expensive, but worth it to me.
Once there were no milk cartons in the recycling, looked for what was filling the bin up now. A dead heat between yoghurt pots and coleslaw pots.
Coleslaw pots - started buying cabbage and carrots and mayonnaise in glass jars. Really easy to make coleslaw! I actually prefer it now. Coleslaw and carrots stay fresh in the fridge for ages, so the coleslaw is always nice.
Yoghurt pots - went onto the internet to find out how to make yoghurt - surprisingly easy! Milk is delivered in glass bottles, I make yoghurt with that, pour it into clean jam jars. Sorted!
Other items have been replaced too. I use washing powder in cardboard boxes, not liquids that come in big plastic bottles. Soap bars instead of showergel. Shampoo bars. Dishwasher powder in cardboard boxes. Soft drinks in cans not plastic bottles (multipacks are usually in cardboard not plastic now).
Have a look at which products are creating the most plastic waste in your household, and pick them off one by one.
Have a look if there are any zero waste shops nearby, where you take your own jars and fill them there. I can get all sorts of things from mine, like nuts, dried fruits, herbs and spices, pasta, flour, coffee, tea, etc. All those 800g mayonnaise jars from making coleslaw come in very handy
.
Hope this helps you see how to make a start, rather than be overwhelmed by the task. Good luck!