A lot of people have said about their Macs slowing down over a period of time. There are a few steps you should take every so often to keep things running nicely.

Onyx

First of all, I highly recommend Onyx. Run this every so often.

When running Onyx, always check the S.M.A.R.T status and Startup Volume. If it needs repairing, you will need to boot from your install CD. Restart with the CD in the drive and hold down the ‘C’ key. From there go to Utilities > Disk Utility > Then select your HDD and ‘Repair Permissions’.

Deleting Cache

Next, I recommend that you delete the files in the following folders, every month or so. ~/Library/Caches and HDD/System/Library/Caches. You may need to restart before you can empty the trash.

Maintenance Scripts

Also, running the maintenance scripts can work wonders. These can be run from within Onyx if you have it, or through Terminal.

Go to Applications > Utilities > Terminal. Then type the following: sudo periodic daily weekly monthly, then press enter and type your password. This will run the daily, weekly and monthly maintenance scripts. (The weekly script will take a while)

Unwanted Files

When you get your Mac, if you haven’t re-installed OS X, you will find there is GB’s worth of language files and hundreds of printer drivers which you may not need. To free up disk space then it is recommended to delete the ones you don’t need.

Printer drivers are located in: HDD/Library/Printers

Language files: Download Monolingual to remove unwanted languages.

De-fragmenting

The most commonly asked question from Windows to Mac users is “Should I defrag my Mac?”.

In short, no. Although some people swear by it, it is not needed. OS X defrags itself. If you still want to defrag, have a look at iDefrag.

Also, to see information about defragging, see this.