OSX handles most of this itself. It's probably better to just let it do its own thing, especially if you're not sure what these different tasks are actually doing. People may recommend OnyX or something similar, but these apps are very powerful and if you're not positive you know what you're doing they can cause a lot of trouble.
Instead, use Disk utility to repair your permissions every now and then. If you're bored, also use it to verify your drive. Calibrate your battery monthly and you'll be right.