I'm not sure what we should do, it's very hard to determine what minimizes harm and maximizes benefits at a global scale. It's certainly not as simple as extremists would like to believe. Certainly it would be much (MUCH) less risky to slow warming as much as possible and maintain constant or slowly reducing CO2 levels.
I think from the standpoint of predicting what will happen, my best guess is that people will use fossil fuels until it is economically not viable to do so. If you want hasten it at an individual level, buy solar panels and have your house disconnected from the grid until fees you pay no longer subsidize fossil fuels. Frown at people and refuse to give them positive social cues when they buy a car that isn't electric. Instead of "oh nice car" just say "it would be so cool if they had a plugin version!". Support electrification of things like heat and water heating so long as it can be powered by non-fossil sources.
In the long run I think solar power, effective battery technology, and the peaking of the global population combine to cause fossil fuel usage to reduce over the next 100 years or so until CO2 levels stabilize. Lots of large CO2 emitters are already leveling off - the output is too high to sustain but at least it's no longer increasing year over year - such as from cement production.
Honestly it's not much but that's what you can do, larger social movements and political action do not work when someone's decision is whether to spend $800 a month or $100 a month to heat their house. Anyone who says it does should buy a thermometer, but instead they will get a plane ticket to the next big city to run around in the street yelling at police (literally the only people paid to not care about your slogans) while nobody really notices.