How do I measure computer performance before and after optimizations?

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How do I measure computer performance before and after optimizations?

I want to either programmatically or manually measure how much PC performance increase I get after using a Windows optimization program. There are several programs on the market that do this and I want to be able to tell which ones do it the best, etc ...

What values within Windows OS are good to use for measuring performance of the computer as a whole?

Should I be measuring application load times? Should I be measuring CPU processing times? I'm not really sure what would be the best way to really figure out how fast and smoothly a Windows machine is running other than simply noticing it visually.

Edit: things usually being optimized are 1) registry, 2) temp files, 3) unnecessary files, 4) empty folders, 5) browser history, 6) defragmenting registry, 7) updating drivers, 8) defragmenting hard drive, etc ...