Don't do anything.
You can repair your permissions via disk utility but odds are you really never have to do that. If something stops working this is a good first step but to do it "just because" is kind of silly.
OS X defragments itself as needed so no need to do that.
As long as you leave your Mac on and it doesn't go to sleep it automatically runs all the necessary maintenance in the background.
If you want it to run smoothly, just let it be.