"The Efficient Mac User" at Low End Mac has listed 11 ways to optimize the performance of your Mac - whether it be a high-end or low-end unit. Yes, some items on that list are pretty simple and well-known, but they're all good basics that any Mac user should know, so we're putting them here as well.

The goal here is to save on RAM and processor resources - even by doing something as simple as turning off or removing unwanted applications and widgets.

QJ.NET also has a guide on troubleshooting OS X from July, 4, 2006 based on an article from Apple Matters. There is also an article on clearing up more hard drive space.

Remove unnecessary code. A significant number of recent software for the Mac are programmed to work with PowerPC processors and Intel processors. If you have a PowerPC processor and don't intend to migrate to an Intel Mac, or if you already have an Intel Mac, then you don't need the software code that lets your applications run on PowerPC! You can look for utilities like XSlimmer that will "slim down" the code on your software.

(For example, my friend Samantha has an Intel Mac, so she uses XSlimmer to strip away the PowerPC code in her applications - this makes her applications run faster. There's a bonus: it also reduces the size of the applications so she saves on hard drive space!)

Clean out startup items. Some applications entrench themselves in your Login Items folder, and that makes these applications automatically open each time you restart or login to your account. Go to Apple Menu > System Preferences > Accounts > Login Items to see a list of these startup items. Click on one item in the list and hit the minus button at the bottom of the list to remove that item. NOTE: Be careful about removing important or critical applications - just remove the ones you know you don't need.

Turn off Universal Access, Bluetooth, Speech Recognition, and Internet Sharing. If you don't use any of these, turn them off (go to the Apple Menu > System Preferences).

Clean out "Other" System Preferences items. While you're in Apple Menu > System Preferences, you can also remove Preference Panes in the "Other" section.

Know the build of your software. If you're using an Intel Mac, you may be better off upgrading your software or application (most likely there's a patch available online). For example, your software may be currently running on the Rosetta translator that lets PowerPC applications run on an Intel Mac. If your application has a patch that can upgrade it to an Intel or "universal" version, then your application won't need to call on Rosetta anymore.

Remove languages and translations. Utilities like Monolingual will remove language localizations that you don't need. As Ed Eubanks Jr. said in his article, chances are you're not using Catalan, Farsi, or Klingon.

Use your fan to have a cooler processor. Any Mac will run more efficiently with a cooler processor. The Fan Control utility lets you set your fan to turn on more frequently - this makes your processor cooler, although it shortens battery life.

Clean out widgets. Even if your Dashboard is hidden, your enabled widgets are running. So take the time to disable the widgets you don't need to free up RAM and processor resources.

Clean up your hard drive. Mac OS and Mac OS X uses free space on your hard drive as virtual memory ("sort of" like RAM). Photos, music, and videos take up a lot of space - you might consider moving them to CDs or DVDs. And be sure to clean out your Trash - Ed Eubanks Jr. said, "One colleague couldn't figure out why her drive was so full - until she realized that she hadn't emptied her Trash in almost four years!"

Use your Activity Monitor. The Activity Monitor in OS X shows you CPU, RAM, and virtual memory use. It also shows you if an application is a PowerPC or Intel build.

Try OnyX and other system maintenance utilities. OnyX, Cocktail, TinkerTool, and other utilities give you a lot of tools to maintain, clean, and optimize your Mac.