Q: Where to get a list of actions to improve OSX 10.6 processing speed?

Slowness in a computer can be caused by many things, mostly a lack of free space on the hard drive or insufficient RAM for the tasks it is asked to do.

As for MacKeeper:

Do not install MacKeeper (and how to uninstall it if you have):

https://discussions.apple.com/docs/DOC-6221

(Please note that references to the original developers, Zeobit, also now refer to Kromtech Alliance Corp, who acquired MacKeeper and PCKeeper from ZeoBit LLC in early 2013.)

I  know it can be difficult to accept but the MacKeeper promotional activity is devious.    Do not engage with it; if the forums warn you it is from knowledge and experience and not to be ignored.

I'm sure Klaus will come in on this too but but these are the minimum requirements to upgrade from 10.6.8 to Mavericks.

OS X Mavericks: System Requirements

Ideally you should have at least 4GB of RAM although Apple say 2GB.

Buy the additional RAM which you can insert yourself.   It is not difficult though it should be approached with care.

Before you download Mavericks (which incorporates Lion and Mountain Lion in its makeup) read the following to check if you have irreplaceable Apps that work with Snow Leopard.

Application compatibility table - RoaringApps

Via the App store you should then be equipped to download Mavericks, but be aware it is a big program and takes time.

So far so good, but you didn't comment on my comments on why computers can run slow!

You should not, IMO, consider upgrading until your Snow Leopard house is in order!

You can check here to see how much memory can be added.

http://eshop.macsales.com/shop/apple/memory/iMac

You need more RAM!

Also, how often do you clean out your caches?

Repairing permissions is important, and should always be carried out both before and after any software installation or update.

Go to Disk Utility (this is in your Utilities Folder in your Application folder) and click on the icon of your hard disk (not the one with all the numbers).

In First Aid, click on Repair Permissions.

This only takes a minute or two in Tiger, but much longer in Later versions of OS X.

Background information here:

http://support.apple.com/kb/HT1452?viewlocale=en_US

and here:

http://docs.info.apple.com/article.html?artnum=302672

An article on troubleshooting Permissions can be found here:

http://support.apple.com/kb/HT2963

By the way, you can ignore any messages about SUID or ACL file permissions, as explained here:

http://support.apple.com/kb/TS1448?

If you were having any serious problems with your Mac you might as well complete the exercise by repairing your hard disk as well. You cannot do this from the same start-up disk. Reboot from your install disk (holding down the C key). Once it opens, select your language, and then go to Disk Utility from the Utilities menu. Select your hard disk as before and click Repair:

http://support.apple.com/kb/HT1782?viewlocale=en_US

Once that is complete reboot again from your usual start-up disk.

More useful reading here:

Resolve startup issues and perform disk maintenance with Disk Utility and fsck

http://support.apple.com/kb/TS1417?viewlocale=en_US

For a full description of how to resolve Disk, Permission and Cache Corruption, you should read this FAQ from the X Lab:

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

Apple's advice on general maintenance:

http://support.apple.com/kb/HT1147?viewlocale=en_US

Agreed with the help you got from others.  Here's some more info on what can slow a Mac down:

https://discussions.apple.com/docs/DOC-6921

Upgrading to 10.7 or later is ill advised until this tip is followed:

https://discussions.apple.com/docs/DOC-6271

Add RAM <http://crucial.com> <http://macsales.com> as much as you can afford or as much as the Mac can hold.

Replace the hard disk with an Solid State Disk (SSD) <http://macsales.com>

These 2 things will give an older Mac a new life.

My only concern with SSDs is have they yet made it possible to securely erase the drive before giving the machine to another individual?   I know there was concern about that in the beginning, as erasing an SSD using the same methods as a hard drive still left behind crumbs that could be recovered a hard drive would not give.