1.Force quitting an app that is not responding
If an application is not responding, if it's continually bouncing in the Dock or appears to have frozen, you may need to force quit it. You can do this by holding Command+Alt+[esc] to bring up the Force Quit window, or by choosing Force Quit from the Apple menu. After quitting the program, try relaunching it. If it still doesn't work it may be incompatible with your version of OS X. Thankfully, force quitting programs on Macs nowadays doesn't generally affect the stability of the system and doesn't require a restart.
2. Fixing software update errors
If you run the Software Update application (which can be found in System Preferences) on your Mac and are presented with any kind of an error, it could be that you need to repair permissions. OS X is based on a system of permissions telling it which user has access to what files. If these become corrupted, your Mac might erroneously think that you don't have the right privileges to run and install software. Go to Applications > Utilities and open Disk Utility. Then, choose your boot drive, this is usually called Macintosh HD, and then click the Repair Disk Permissions option. After this process has been completed, try the software update process again. Everything should be running back to normal just by going through this simple process.
3. Opening files in specific programs
If a file or document is refusing to open but you know which application it should work with, try holding Command+Alt while dropping the file onto the relevant application's icon, either in the Dock or in Finder. This should force your chosen application to open the file. It will also force any application to try to open a file, though success rates will vary. Alternatively, select the problem file and press Command+[I] to open up the Get Info window. Then, choose Open With: and, from the pull-down menu beneath that option, pick an application to open the file. To make every file of that kind open with that application in the future, click the Change All... button.
4. Making some space and adding more RAM
If your Mac is feeling sluggish and simple tasks are taking longer than usual to do, check that the boot drive isn't getting too full by selecting it and pressing Command [I] to Get Info on it. Look at its size and how much available free space is left on it. If it's less than 20% of the drive's size that's free, you'll need to offload some stuff either onto DVDs or onto external hard drives to free up space. Good candidates include movies, iPhoto and iTunes libraries, plus any applications you don't use much. Also look at fitting more RAM to your Mac as this will also help greatly with performance.
5. Ejecting a disc that's stuck in your Mac
If a CD or DVD refuses to eject, and it's definitely not in use by any programs, try restarting the Mac whilst holding down the left mouse button. This should force the opening of all optical drives and eject your troublesome disc. You could also open Terminal and type drutil tray open, then hit [Enter]. If other devices like USB or FireWire hard drives, memory sticks or iPods refuse to eject, the safest course of action is to shut down the Mac, disconnect the device and then restart. Often, a device will then behave normally.
6. Finding a file that's missing on your Mac
We all like to think that we're super organised by storing our documents and files in relevant folders on our Macs, but every now and then we forget to put them somewhere sensible and a file ends up somewhere completely obscure. If you can't find a file or folder that you think may be somewhere on your Mac, you can use Mac OS X's built-in Spotlight search system to find it. Click on the Spotlight icon (small blue circle with a magnifying glass inside) at the top-right of the menu bar and type the name of the file or even just part of its name. From the resulting list you should be able to see the missing file and open it as long as it's on your Mac, of course! Alternatively, press Command+[F] to open the search window, and run a search based on its filename and also date opened, date created, file type or any of the available criteria. The more information you can enter, the easier the search will be.
7. Resetting your admin password
Forgetting your Administrator password can be a real pain when you want to install a new piece of software or run Apple's Software Update application. If you have a vague idea of what the password is you can try entering it, but if this doesn't work you will have to boot the Mac from the OS X install DVD that came with it, by restarting with the disc inserted in the optical drive whilst holding the [C] key down. Then select Utilities > Reset Password and choose a new one. When you reboot the new password should be working.
8. Detecting a second or external monitor
If you connect a second screen or external monitor but it isn't recognised, try using the Detect Displays button in System Preferences > Displays. The port may be set to use a resolution that the screen doesn't support. If this doesn't help, restart whilst holding down Command+Alt+[P]+[R] until you hear the startup chime twice. This resets the PRAM and often forces the Mac to scan its ports and look again at what is connected. This usually brings the monitor online. It also helps with forcing a Mac to recognise external audio devices.
9. Getting back your lost Airport connection
It's always a pain when you want to work over a wireless network but you can't get a connection. If you lose your WiFi connection, check to see that AirPort hasn't accidentally been switched off. Or, go to System Preferences > Network and, from the AirPort > TCP/IP section, click the button called Renew DHCP Lease, which may fix the problem. Another reason for the loss of signal could be that you have simply wandered out of range of a network, so click the AirPort icon to see if the network is still available. If all else fails, try logging out and in again or even restarting, as this sometimes cures any glitches with AirPort.
10. Fixes for viewing WMV files
The web is awash with video formats and not all of them are particularly Mac friendly. The one you're most likely to encounter is Windows Media Video. Download media converter, a software that change WMV files to enable the Quick Time Player to read . Alternatively, download the VLC Player from the disc. It can play back many weird and wonderful video formats, though it's not the world's most elegant piece of software.