Use use the donation ware software called Yasu because it uses well known built-in Unix commands with simple check boxes. Just let the program reboot you mac. Then upon that reboot immeadiatly manually reboot again to completely rebuild your startup/shutdown system cache.
IMHO doing this kind of cache cleaning should be done once about every three or four months. It will keep OS x running almost like new if you do this regularly.
I add good opinions about both OnyX, and YASU.
There's other free apps that will clean out your caches effectively.
No need to pay for one just for that.