There is little you can do except to be informed.
Read post #4 here and pay attention to spectreA, spectreB, and meltdown as described:
Then, purchase a system that has a current processor, i.e 7th, 8th, or 9th gen, making certain that the system manufacturer has an updated bios that addresses the microcode fix.
The other concerns are addressed in the operating system.
One thing you can do is to run this: GRC | InSpectre this link is provided for your convenience and the tool will tell you where you stand with respect to spectre and meltdowm
Last, here is a list of intel processors affected: https://newsroom.intel.com/wp-content/uploads/sites/11/2018/04/microcode-update-guidance.pdf
This does not mean that the bios manufacturer for those boards/systems containing such processors has done or will do a bios update.
And, yes, many,many processors are affected, not just Intel: https://www.techarp.com/guides/complete-meltdown-spectre-cpu-list/