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.
Improve the insulation in your home (loft, cavity wall etc etc)
Require new homes to be built with higher standards of insulation and heat pumps for heating.
Require new homes to be built with solar panels.
Divest any investments (pensions, savings etc) away from funds that contain oil and other polluting companies.