Recently i was having some problems with iTunes 12 on Yosemite and iTunes wouldn't respond after a while or iTunes would just crash when playing a podcast or search the iTunes store.
But there is a simple fix via the terminal following this kb article from Apple for resetting the Sync services :
Fix from apple: http://support.apple.com/en-us/TS1627
OS X Mavericks 10.9.3 and Later defaults delete com.apple.SyncServer SyncServicesResetWorldRunOnce
Quick Look is one of OS X's best features. Hit the Spacebar when you select a file, and you'll see a preview of that file without having to open up an app. It's great, but you can't select any text when you're in the preview.
You can use the following terminal command in the OS X terminal app to enable text selection in Quick Look:
Sometimes you need to see hidden files and folders in your system,
You could use the terminal:
defaults write com.apple.finder AppleShowAllFiles -boolean true
killall Finder
The reverse is
defaults delete com.apple.finder AppleShowAllFiles
killall Finder
For sometime, years? I've been seeing these ._ files on my desktop when browsing files with coda, or an other ftp/file browser where you can see hidden files. Especially on the desktop I see a bunch of ._ file names that are greyed out (._index.html, ._photos.html, etc.). What are these files? How can I get rid of them?
The ._ files are created when you copy or otherwise create a file with metadata or extended attributes on a file system that doesn't natively support it.
Sometimes an application won't start as a result of wrong/corrupt permissions.
Whenever that happens you can unistall, repair permissions and reinstall the software...
But when you have no time and are on a deadline you can try launching the application after temporarily enabling root user on your machine.
You can find steps to enable root user here: http://support.apple.com/kb/ht1528
Ever wanted to know what was was that process eating all your cpu time, here is an easy overview of the processes running on your mac. http://triviaware.com/macprocess/all#Z