If recovering space on your HD matters....

[Dreambird]

I've gotten into exploring things online... just curiosity. Now and then I get a helpful hint. These are things I've found if you happen to be someone who is short of space on their HD and needs to recover as much as they can now and then. I'll keep this thread updated if and when I find more ways to do that w/o hosing your system...  I hope some will find it helpful... 

This next one is only about 132mb on my machine but some people have bigger ones.... around 750mb or so. Go to:
YourHD/Library/SystemMigration
... and look through it. It's where OS X put stuff when upgrading from a Classic Mac OS where things were allowed to be put in places no allowed in OS X or parts of apps that don't comply with OS X standards. When you look through it if you spot something you could still use you can drag in out.
https://forums.macrumors.com/threads/system-integrity-protection-migrated-files.1924234/
... a good discussion on the matter.

Then: YourHD/Library/Application Support
If you look through the folder you may find old PPC apps that are still there but have a "crossed out" overlay on the icons. They won't run and can be deleted. That location sometimes has a few although they may be elsewhere too... In that directory I found 3 apps for my HP Printer that are PPC and will not work. I found most in the above mentioned folder. Depending on what you find it may save a bit of space.

[Xairbusdriver]

There's a not too well known "Storage Management" collection of functions built into the rarely used System Information menu (option-click the black Apple icon in then Menu Bar). To open those functions, use the System Information->Window->Storage Management item (command-U). The four functions are:

• Store in iCloud (instead of on the HD)
• Optimize Storage (mostly concerns email attachments and previously watched iTunes TV shows and Movies)
• Empty Trash Automatically (after 30 days)
• Reduce Clutter (easily sort by last date used plus three other options)

BTW, I'm not sure if these functions were in El Capitan, they are in macOS 10.13 High Sierra, and I suspect in macOS 10.12 Sierra.

While not pointing out any PPC apps (it's been several OSes since I ran any of those!), the upcoming switch to 64-bit apps requirements is just around the proverbial corner; probably 10.15 (it's being delayed once again...). That's usually the reason I check the System Information/Software/Applications list.

[Dreambird]

Thanks, Jim,
I can't find it here on El Capitan, it probably isn't available on this OS.

I haven't run any PPC apps in years either the apps I found were in the directory I posted and were most likely just either old apps related or supporting my printer and apple script.

[Dreambird]

Remove duplicates in your iTunes library.
They're easier to sort out if you've gone first of all in the menubar to File>Library>Show Duplicate Items and then showing them all by Name. Choose the one you want to keep, deleting the other.

Good idea to back up the Music Library in case a error occurs.