If you, for example, install multiple media player applications on your Android device, you’ll find that Android will give you the choice of which application to launch by default when you open a media file or document. However, you may later want to change this default setting.

To do so, go to Settings > Applications > Manage applications and then press the "All" tab. Choose the application that you previously selected as default, and scroll to the section "Launch by default" and press the "Clear defaults" button. Next time you open that particular type of file in the future, Android will prompt you again to choose a new default app.

Ever surfed for the number of a pizza place on your iPhone and just wanted to dial the phone number straight from the webpage? If you are using the default browser on your iPhone, which is Safari, that's no problem at all.

Safari automatically converts numbers that look like phone numbers into links. If you press those links, a popup window will appear giving you the option to call the number from there or cancel. No need to write down or even copy and paste the numbers.

If you are using Internet Explorer and Windows 7, you may have noticed that when you mouse over an IE browser window, a preview of the open tabs in the browser is shown. While this is useful to give you an idea of the sites you have open, it can get annoying if you have multiple tabs open at the same time. If you would prefer to disable this feature, you can.

Just go to Tools > Internet Options (in the upper right-hand corner of the browser) and then click on the "Settings" button in the window that pops up. In the list of Tabbed Browsing Settings, uncheck "Show previews for individual tabs in the taskbar." Click on OK and you should be good to go.

A very useful feature in Microsoft Office is called "AutoRecover", which automatically saves your document at specified time intervals so that in case of an application or system crash, Office can recover its latest version.

By default this is set to 10 minutes, but you can change this easily by clicking on the Office button within the application, and then clicking on the "Word Options" or "Excel Options" (or other application) button in the lower right hand side of the window. Go to the "Save" section and look for "Save AutoRecover information every…" and change the settings there. Be sure to click "OK" to save your preference. A word of caution: setting the interval at very short timespans such as every 1 minute can slow down your computer with frequent writes to the hard disk. Try a number between 5 minutes to 10 minutes first.

Leaving your computer for a short time but don't want anyone peeking at your desktop or files? Simply lock it. When you lock your desktop, anyone who wants to use it will have to log in using their username and password.

One way to do this is to press Ctrl+Alt+Del and then click on "Lock Computer." A quicker way is to press the Windows logo key and the L key.

In Microsoft PowerPoint 2010, you can set an animation to trigger when you click on an object. This is a simple way to add and control interactivity to your presentation. To add an animation trigger, select an object that already has animation applied to it.

On the “Animations” tab, in the “Advanced Animations” group, click “Animation Pane” and then select the animation that you want to trigger. Back in the Advanced Animation group, click and hold on “Trigger” and select “On Click of” and select the object for which you wish to trigger the animation when clicked.

With Windows 7, there are easier and faster ways to rename multiple files in one sweep. The first way is to click on a file's name and rename it as usual, then press the "Tab" key to access the next file in the list.

Another way is to select multiple files (press the Ctrl key or Shift key and select the desired files), then right click on the first file and choose "Rename" to give it a new name. The rest of the files will be renamed with the same name. For example, if you name the first file "image", it will become "image (1)" followed by "image (2)" and so on.

Google Chrome allows you the option to search within a specific site. First type the web address of the site you want to search in the address bar, and then press the "Tab" key.

If Google Chrome has a record of the site's search engine, you’ll be offered the option to search within that site only. Try it with sites such as LinkedIn, Bing, and Yahoo.

In Windows, there are various options for configuring the speed, look, and behavior of your mouse pointer to exactly the way you want it.

To do so, click the Start button, and then click Control Panel. Click Hardware and Sound, and then under Devices and Printers, click Mouse. In the Mouse Properties box, click on the Pointers and Pointer Options tab, and adjust the options to change the shape and size of your cursor by changing the "scheme". In the "Pointer Options" tab, you can change the speed, visibility, and other characteristics of your pointer. You can add pointer trails, automatically snap the pointer to buttons and dialog boxes, and so on. These settings are especially handy when using small screens such as on laptops or netbooks.