1.  Turn on Screen Zooming.

This is perfect for live demos and presentations.  Open System Preferences > Accessibility > Zoom.  Click “Use scroll gesture with modifier keys to zoom:”.  Hold down the control key and run two fingers up or down the touchpad.  (More here.)

Universal Access > Accessibility Showing Zoom Settings

 2.  Use Full Screen Mode.

Almost every window can be maximized to take over the full screen.  Hit the arrows in the upper right corner of the window to expand it.  Hit them again to shrink it back to the regular size.

3.  Show All Windows with F3

This is an awesome productivity feature: with any window open hit F3.  You’ll see a list of all windows so you can quickly switch between them.

Mission Control

4. Hit Spacebar to Preview.

Ever had two versions of a file but aren’t sure  which one you want?  Click on the file then hit Spacebar.  You’ll see a preview of the file on your screen.

5.  Search using Spotlight

The magnifier glass in the upper right corner of the screen is your friend – click it, then type.  It’ll let you find anything on your entire computer.  Not sure where you saved it?  No problem.  Just use spotlight.

Spotlight - Upper right.