Collective:

-Regulate Polluting Industries

-Improve insulation in older buildings

-Build more apartments

-Put carbon labels on products

-Mandate higher build quality of manufactured goods

-Require that water pipes have pressure management and active leak detection

-Prioritize public transit over electric cars

-Halt all new road developments and just maintain them until public transit is good enough

-Subsidize Electric cars (second to public transit in funding)

-Establish support networks for people who are using older gadgets/cars/clothing to encourage solutions to make goods last longer

-Build more green spaces

-Create a program to recycle old clothing

-More widespread use of contactless payments

-Ban all fossil fuel ads

-Ban oversized vehicles

-Encourage the use of hatchbacks and sedans

-Towns sign plant based treaty

-Convert animal agriculture land to wild lands

-Ban private jets/yachts

-Design cities as more walkable

-Switch to renewable and nuclear technologies

-Support repairability

-Shut down all oil operations

-Mandate microfibre filters for washing machines

-Force companies to mine minerals from e-waste instead

-Give up half of the planet to nature

-Do everything to prevent and end wars

-Tax the rich and use the money for climate initiatives

-Switch to bidets to save trees

-Switch to super slippery toilets to save water

-Mandate all stoves to be electric

-Reduce concrete in constructions projects and opt for bamboo/wood construction

-Require all office work to be done from home for as much as possible

-Ban discrimination and promote affirmative action so that there isn't lost potential or innovation from disadvantaged groups

-Increase grid interconnections

-Implement waste-to-energy conversions for waste management systems (stopgap solution)

-Build robust high sped rail network and ban flights under 4 hours.

-Require much longer warranties on consumer goods

-Require all software to become open source after the company stops developing the code

-Patents expire after 4 years

-Ban cryptominning

-Increase energy efficient standards with new houses with solar panels mandatory

-Support political parties with green policies

-Boycott fossil fuel banks and switch to green credit unions

Individual:

-Switch to E-sim

-Switch to green burials

-Buy used

-Install geothermal heat pump systems

-Install smart thermostats

-Use shampoo/conditioner bars

-Shop at refillable container stores

-Buy stuff at the local store

-Eat plant based

-Switch to Ecosia

-Recycle

-Give homemade gifts

-Compost

-Be organized

-Avoid synthetic cloths

-Buy reputable carbon credits

-Install Linux on new/old computers

-Pickup litter

-Ride your bicycle instead of the car

-Adopt kids and companions instead

-Start your own garden

-Use older cars for more than 12 years

-Keep phone for longer than 5.5 years (easy to do with fairphone,iphone, pixel, samsung or android phone with unlockable bootloader)

-Buy Fairphones as they're the most repairable and have to 8-10 years of software support

-Buy Framework laptops as they're user repairable upgrade-able

-Use reusable diapers for your infant/toddler

-Buy goods within your continent to avoid cargo ship bunker fuel

-Use refillable water bottles for everywhere you go

-Demand that your investment/retirement program switches to green projects

-Switch to e-documents

-Track your government's climate policy by visiting https://climateactiontracker.org/countries/

I will add more to list as more ideas are thought of.