Do exercise, strength training, cardio. Bodyweight stuff or yoga is great for everyday life activities. How far can you carry 60 pounds of supplies and equipment?
Make friends, obviously.
Learn how to resolve conflict non-violently. You and everyone else will constantly be running into conflicts and someone is going to have to remember how to meet everyone's needs without killing people.
If you don't already work in an industry that is doing research towards or creating a product that makes a difference, change careers. The solution to this, both on an individual and collective level, is not to give up and hide in a hole hoping you die quietly in your sleep. The solution is to fucking solve the problem.
We need smart people in engineering, nuclear science, agriculture, bioscience, and politics. People that give a damn and aren't satisfied to sit on their asses and wistfully dream of eco-primitivist utopias. Put your resources into skilling up and move to a center where shit is getting done. Talk to people that are working on the problem and find a job that is actively moving the needle.
If we can't fix it then at least you'll die trying rather than cowering.
The question is, how many people do you want to sacrifice to eat your delicious cow and drive a SUV?
What you as an individual can do to prepare is put pressure on the suppliers of goods and services (including your government) to take their role seriously and reduce emissions. Stop using single-use plastics, stop buying groceries that are individually shrink-wrapped. Buy fresh fruit and vegetables and prepare your own meals. Walk where you can, try to use public transport for commuting (it takes longer, but someone else is driving so you can do your morning and evening reading & correspondence on the bus/train)
Basically do everything you can to reduce your energy consumption, both directly and indirectly. Energy consumptions is a very good proxy for personal contribution to emissions, including the embodied energy in things like plastic utensils and fast food wrappers/boxes/bags.
Rather than watching a movie on Netflix, read a book. The internet services and domestic devices used to watch a movie will consume more energy during that movie session than a year of reading on a tablet or paper books (with a bed lamp book light).
Apart from overpopulation, the biggest contribution to global emissions is the extreme energy consumption lifestyle of western countries. We offshore a lot of the production and point the finger at China, but China’s emissions are mainly from manufacturing and transport which is mostly for products being sent to western countries.
Try to get rich enough before the worst effects become widespread that you can buy your way out of some of it.
I believe that in our lifetime we will see the western countries effectively barricade their borders. When an unannounced ship approaches with desperate human beings on board, fleeing the wars, we won't be even allowed to think about accepting them. The ships will be, not stopped and turned around, but torpedoed and sunk on sight. The corpses will be harvested for feed and fertiliser.
From that point onwards, in another couple of generations, there won't be any sanctuaries left. Not even for the richest. They will all have been overrun, pillaged and plundered.
My only consolation is that I am old enough to not necessarily witness all of it.
How do you, as an individual, prepare for this?