Best Way to Clean Mac Cache, Temp and Log Files

Besides Kurt's recommendations occasionally boot into Safe Mode by booting with the Shift key held down and reboot normally.

NOTE: Safe Mode boot can take up to 10 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

Unless you're seeing an issue with how your Mac is running, there's no real reason to ever do this. Caches exist to speed things up. Temp files are taken care of by the apps (or OS) they belong to.

Just shutting down your computer at the end of the day does a lot of this work for you. Then next time it's turned on, the OS trashes a lot of junk that may have been left on the drive by an app, or apps, that aren't running.

Otherwise, you can restart into Safe Mode (restart and hold down the Shift key). Besides checking the file system for errors and some other tasks, it tosses all of the cache data and other files of the user account you logged into in Safe Mode. Then, just restart again normally.