To see if there is cleanup to be done:
DISM /Online /Cleanup-Image /AnalyzeComponentStore
To remove obsolete and unused system files:
DISM /Online /Cleanup-Image /StartComponentCleanup
To remove obsolete and unused system files and also service pack uninstallation files:
dism /online /Cleanup-Image /SPSuperseded
To remove obsolete and unused system files and everything prior, making it impossible to reverse any patches:
dism /online /Cleanup-Image /StartComponentCleanup /ResetBase