See also: Isolating issues in Mac OS X at
MalwareBytes - Virus and other malware
EntreCHeck - comprehensive diagnostic report
 on the current state of your computer. 

Strange behavior:
This can be:
1.  A slow system.
2.  Apps hang
 (i.e. you just get a spinning beach ball
  when trying to start an app or do something.)

What to do:
How to Reset Your Mac's PRAM or NVRAM (Parameter RAM) - How to reset a Mac’s NVRAM, PRAM, and SMC - M1 processor No PRAM or NVRAM reset Reset SMC On a laptop close the lid for 30 sec.

Maintenance at titanium software OnyX is a multifunction utility that you can use to verify the structure of the system files, to run miscellaneous maintenance and cleaning tasks, to configure parameters in the Finder, Dock, Safari, and some Apple applications, to delete caches, to remove certain problematic folders and files, to rebuild various databases and indexes, and more. -

Start "Disk Utility" in utilities and run "Verify Disk".
If there are errors you need to run Repair Disk 
(see tips for the procedure).
Crete a new account in "System preferences" > Accounts : Click on "+" Login to the new account. If no problem here it is probably something in your user Library folder. Try an archive and reinstall. This worked to fix a problem where multiple finger track pad gestures didn't work on my account after I installed files from my old mac with Migration Asst. However you may need to reinstall without restoring user setting which may cause other problems. See Preference Restoration. Can't see servers on OS X 10.4 Turn off Firewall in: "System Preferences" > Sharing > Firewall Startup problems
- Boot to "Safe Mode" (Safe Boot) by holding the shift key from chime until you see "Safe-boot" on the progress bar box. This disables a lot of functions (kernel extensions) and runs a fsck in background.

- Boot to single user mode. Hold Cmd-S at startup. You can then run fsck or fsck -f.
- Select System by holding optn at startup.

See Magical Macintosh Key Sequences
Hardware test- Insert Applications Install Disc 2 (Intel macs shipping with 10.5.5 or later) Restart your computer, holding down the “D” key

How To Troubleshoot Your Mac

Intel vs Power PC Processors. Around 2006-2007 Apple switched from Power PC to Intel processors in new Macs.

Developers were encouraged to write "Universal Binary" applications which had native code for both Intel and Power PC processors.

They also included software called "rosetta" in intel Macs which would translate Power PC code to Intel code.

According to Apple, applications with heavy user interaction but low computational needs (such as word processors) are well suited to translation via Rosetta, while applications with high computational needs (such as raytracers or Photoshop) are not.


Free up storage
Sync iPhone and Mac
Use Continuity to connect your Mac, iPhone, iPad, iPod touch, and Apple Watch
I was able to sync a backup of my phone, on to my Mac through iTunes. I then erased the phone and all my data (through settings in the phone itself) and restart it as a “brand new” phone. turned off & back on again, plugged it into the Mac and it gave me the option to “restore from backup” After I got the phone back to its old self it was totally in sync with the desktop for messages and the like.
See also:
Apple Tech Exchange:
MacFixIt troubleshooting solutions for the
Mac Resource Page:
MacCentral Macintosh users news and
How To Troubleshoot Your Mac
Restoring User Library Files

last updated 6 Feb 2009