General Tips

Autocomplete
When typing in your favourite mail application or text editor, simply press the esc key after typing a few letters to see a list of possible word endings.

Zoom
To zoom anywhere in mac os x, simply press command+option+8 keys to activate it then press command+option and + or - to zoom in or out. These settings can be further managed in the universal access area of the system preferences.

Quickly force open your files
If double-clicking a file doesn't launch the application you want to use, just drag your file over the desired program in the dock while holding the option + command keys to force any application to open any file you like.

Quick dictionary
Rather than opening the dictionary application to check on a word, simply hold down the command + ctrl + d keys on your keyboard and hover over any word in your favourite web browser, mail application or text editor to display an on the fly definition pane.

Multi-session burning
If you want to burn a cd and add something to it again later, just check the "leave disc append able" checkbox to leave the disc open for another session.

Forgot a password?
If you have forgotten a password for a network, a website, or almost anything else for that matter, just open your keychain application in the utilities folder. Keychain keeps a record of your passwords, which can be displayed simply by entering your administrative password.

Widgets?
Dashboard widgets, like web pages, are capable of many different things, often to perform tasks that would be tedious or complicated for the user to access manually. One example is the google search widget, which simply opens up the user's browser and performs a google search. Other widgets, like wikipedia, grab the contents of webpages and display them within dashboard. Some widgets can also serve as games, using adobe flash (or another multimedia authoring program) to create games just as if they were in a browser. But be careful! These applications can be addictive!