Boosting memory is the primary thing to start with.
The easiest way to do that is increasing the RAM of your Mac. Selection of the suitable RAM is essential to upgrade the performance to the next level. It is essential that you select a proper RAM card that suits the user and system specifications. To start with, you can download free programs like MacTracker which provides you with detailed technical specification and helps you choose the right RAM card.
Installing of faster hard drive is another primary requirement for optimizing your system. The speed of the hard disk helps to yield better results and increases the overall performance. Ideally a hard drive with an rpm of 7,200 is recommended but you can also opt for hard drives with higher RPM.
Boost the application processing speed by not opting for non required additional features and languages which you can do by simply deselect them while installing. Always choose custom install for superior memory management.
Use FireWire instead of USB port, although USB is quite cheaper than FireWire still it fails to offers high data transfers and higher performance as compared to FireWire.
Opt for the G4 and G5 based Mac as they come with processor bus slewing feature by which you can manually increase or decrease the power of CPU. This features helps in power management.
Keep the above tips and tricks in mind and definitely you can optimize the perfect system for your Mac in no time.