Make a category called OS X. Specify a criteria. Don't specify a file type. Specify a folders (up to 4) - Now enter the OS X system folders, like "system", "user", "library", etc. Since I never use Classic or any OS 9 stuff, I put anything in the "System Folder" and all OS 9 stuff at the bottom of the sorting list. I made another category for the Apps I often use like Mail, iTunes, Internet Explorer etc. I named it FaveApps put it 2nd in the list. I made the free space category the 3rd item in the list.
After I optimised using this profile, I found the beach ball would appear much less frequently. Since I don't have another partition for my swap file, I don't know if this is better than that technique for killing the beachball.
[Editor's note: I have never used Speed Disk so I can't vouch for the effectiveness of this particular tip.]

