So I recently turned on my iMac G4 800MHz for the first time since August 2015, and it was ungodly slow. So I decided to fix that. Below are a few things I did to improve it.
Software Update
This is a huge roll in making sure you are running the latest, for performance and security. Go to the Apple Logo then “Check for Updates” and if any are available, install them!

Also disable automatic update checks, and if you have iWork or iLife, be sure to check for updates manually.

Also to save a bit of time if you are starting with a fresh install of Tiger or running an earlier version of Tiger, download the 10.4.11 Combo Update (180.8MB) and keep it handy for future usage.
Install TenFourFox
This is important because the tweaks and extensions you can enable under TFF will make your life easier, especially with the big push to HTML5.
Download TFF here. Be sure to select the correct processor!
Install AdBlock. This will also make webpages load up faster. <--- I would suggest BluHell Firewall over AdBlock, AdBlock Plus or AdBlock Edge. The AdBlock addons have a serious memory leak and are big heavy CPU users.

TenFourFoxBox
If you have a frequent webpage that you visit and want to access it quickly while also having it load up quickly you can use TFFB to make an app of just that webpage.

Install TenFourFox Tweaks (by @eyoungren and @Altemose)
I use this particular script on all my PPC machines as I notice a nice improvement in how pages load and every little bit helps. Take a look at the thread here.
Disable Spotlight and Dashboard
Both of these are great features I love to use on my G5, but they are so resource intensive the G4 can’t handle it all that well and disabling them will greatly help the machine performance.
Disable Spotlight: Open terminal and paste:
Disable Dashboard: Open terminal and paste:
Disable some effects in the UI
This also taxes the systems resources so I would recommend turning them off.
Disable Dock Magnification
Set “Minimize using:” to Scale Effect
Uncheck “Animate opening applications"
----- ADDED -----
Install and use Onyx for Tiger. Use it to set display of sheets to Very Fast as well as to set other parameters you cannot ordinarily set via normal methods.

Remove Extra Languages and Intel Code
Each application from the Tiger/Leopard era included code in “universal apps” which would work with both Intel and PPC and also extra languages. Removing this will reduce the size of the program and will also speed up the program as it is a smaller app.
Run Monolingual 1.3.9 (download on the PPC Archive Utilities page) and click “Run”

So now my iMac G4 800MHz is a bit happier. I'm sure not all of these tweaks are needed on a dual processor G4 or any G5, but certainly something to consider if you have a single processor G4. Enjoy!
--
This is a Wiki post so feel free to add anything you think would be fit
Software Update
This is a huge roll in making sure you are running the latest, for performance and security. Go to the Apple Logo then “Check for Updates” and if any are available, install them!

Also disable automatic update checks, and if you have iWork or iLife, be sure to check for updates manually.

Also to save a bit of time if you are starting with a fresh install of Tiger or running an earlier version of Tiger, download the 10.4.11 Combo Update (180.8MB) and keep it handy for future usage.
Install TenFourFox
This is important because the tweaks and extensions you can enable under TFF will make your life easier, especially with the big push to HTML5.
Download TFF here. Be sure to select the correct processor!
Install AdBlock. This will also make webpages load up faster. <--- I would suggest BluHell Firewall over AdBlock, AdBlock Plus or AdBlock Edge. The AdBlock addons have a serious memory leak and are big heavy CPU users.

TenFourFoxBox
If you have a frequent webpage that you visit and want to access it quickly while also having it load up quickly you can use TFFB to make an app of just that webpage.

Install TenFourFox Tweaks (by @eyoungren and @Altemose)
I use this particular script on all my PPC machines as I notice a nice improvement in how pages load and every little bit helps. Take a look at the thread here.
Disable Spotlight and Dashboard
Both of these are great features I love to use on my G5, but they are so resource intensive the G4 can’t handle it all that well and disabling them will greatly help the machine performance.
Disable Spotlight: Open terminal and paste:
Code:
sudo launchctl unload -w
/System/Library/LaunchDaemons/com.apple.metadata.mds.plist
sudo launchctl unload -w /System/Library/LaunchAgents/com.apple.Spotlight.plist
Code:
defaults write com.apple.dashboard mcx-disabled -boolean YES; killall Dock
Disable some effects in the UI
This also taxes the systems resources so I would recommend turning them off.
Disable Dock Magnification
Set “Minimize using:” to Scale Effect
Uncheck “Animate opening applications"
----- ADDED -----
Install and use Onyx for Tiger. Use it to set display of sheets to Very Fast as well as to set other parameters you cannot ordinarily set via normal methods.

Remove Extra Languages and Intel Code
Each application from the Tiger/Leopard era included code in “universal apps” which would work with both Intel and PPC and also extra languages. Removing this will reduce the size of the program and will also speed up the program as it is a smaller app.
Run Monolingual 1.3.9 (download on the PPC Archive Utilities page) and click “Run”

So now my iMac G4 800MHz is a bit happier. I'm sure not all of these tweaks are needed on a dual processor G4 or any G5, but certainly something to consider if you have a single processor G4. Enjoy!
--
This is a Wiki post so feel free to add anything you think would be fit
Last edited: