It takes a lot of mental bandwidth to think about lowering your own CO² emission. Still useful in terms of awareness though! Less driving and flying, less meat, low cost/high reward home energy efficiency improvements, ... are quite obvious ways.
It's important though not to overlook the effect of investing in other people's carbon efficiency instead.
A piece of anecdotal evidence. I willingly spent ~25000€ extra on my Belgium home's energy efficiency. One year later, I end up living in Latvia, where many places don't even have simple radiators valves. When their appartments with city heating get too hot in winter, they just open the window at -30°C! Imagine spending just 5000€ on my home, and the rest offering free radiator valves installations in Latvia -- or other even more efficient schemes of course!
https://en.wikipedia.org/wiki/List_of_countries_by_carbon_di...
