The Short Answer: Aside from practicing "normal" safe computing (don't open suspicious email, avoid unknown websites, blah-blah) there is nothing YOU can do except wait for the software and hardware geniuses to develop solutions.
- There is an incredible amount of misinformation on the internet about Meltdown and Spectre vulnerabilities and it is easy to become overly concerned and confused. As of this writing, there have been no known attacks.
- ALL computing devices (computers, tablets, smartphones, servers, virtual PCs, virtual servers, etc.) are possible targets.
- Any software that uses the special area of any processor to cache (store data or instructions to speed up processing) is a target.
- Specific brands of processors have been falsely identified as the most likely to be open to these vulnerabilities. See item #2.
- At this time, at least one firewall manufacture is claiming their equipment is mitigating Meltdown and Spectre for the devices sitting behind their products. Based on my research, that claim is misleading at best. Even if the claim was true, when you take your laptop or phone out of the protection zone, you have lost your protection. If you bring your infected computing device into the protected zone? Well, it's still infected and at this moment we aren't sure what that means to the rest of the computers in the protected zone.
- At this moment the speculation is that the "fix" is going to be a combination of software and hardware patches. The software patches may have to be designed for every modern operating system. The hardware patches may have to be designed for each different processor. Then, somebody is going to have to determine what to install on individual devices, then do the work. Sound expensive?
- Further speculation is that there will be an "unknown" hit to the speed of your computing device. Possibly severe. How can you be certain of that when the patches haven't been developed?
Conclusion: Let's hope this is like "Y2K" and much ado about nothing. Let's not worry about what we don't control. Let's keep our computing devices patched as recommend by our hardware and software vendors. Let's recommit to practicing "safe" computing.