I have quite a few ways, probably can't remember them all.

Reusable toilet paper
only buying pink sticker stuff at the grocery store
get free day old bread from nearby bakery
no gf
no car
live in the slums to save money on rent
bring a thermos to work rather than buying tea all the time at tea shops
only buy clothes at thrift stores
no internet/netflix/cable/amazon/newspaper subscriptions/etc

do you have any?