Generally, OSX does a really great job of keeping up the drive performance. There really isn't much you need to do. It doesn't hurt once in a while to run the "repair disk" and "repair disk permissions" from the recovery partition. You can also download a free app called Onyx that does a good job.
If you are running Bootcamp with Windows, then you can defrag that partition from within Windows, but only do this if you are running a regular mechanical platter hard drive. If you have a Solid State Drive, then defragmenting is not necessary and supposedly can damage the drive as well. So don't do it if you have a SSD in your machine.