Ask HN: Personal carbon offsets

I’m interested in attempting a carbon-neutral life. I’ve noticed that Enterprise car rental has an option to buy a carbon offset for a car rental for a surprisingly small fee (less than $2 a day). And one can also purchase carbon offsets for flights. But I don’t know how reputable or effective these are. Obviously it’s best to emit less - use less electricity, use public transit, etc. but that’s not a complete solution. What’s the best, most cost-effective way to offset your own carbon emissions?