Q: maintenance, cleaning up things slowing down the computer

Mac OS X tends to look after itself...

To keep your Mac Happy... See Here...

http://support.apple.com/kb/HT1147

http://www.thexlab.com/faqs/maintainingmacosx.html

Mac OS X: About background maintenance tasks

Every once in a while -

Disconnect all peripherals from your computer.

Boot from your install disc & run Repair Disk from the utility menu. To use the Install Mac OS X disc, insert the disc, and restart your computer while holding down the C key as it starts up.

Select your language.

Once on the desktop, select Utility in the menu bar.

Select Disk Utility.

Select the disk or volume in the list of disks and volumes, and then click First Aid.

Click Repair Disk.

Restart your computer when done.

Repair permissions after you reach the desktop-http://support.apple.com/kb/HT2963 and restart your computer.

Depending on how you use your computer and the age of same, every few months or so run Diskwarrior.

You're Welcome