Transitioning from Windows to the Mac and I miss the dedicated PageUp, PageDown, Home and End keys. So I'm always having to re-remind myself how to do those things on a Mac:
PageUp: hold down the Fn key and press the up arrow key
PageDn: hold down the Fn key and press the down arrow key; or press the spacebar
Home: hold down the Fn key and the Option key, and press the Up arrow key; or hold down the Command key and press the left arrow key
End: hold down the Fn key and the Option key, and press the Down arrow key; or hold down the Command key and press the right arrow key
Drives me crazy that the Mac couldn't just put those dedicated keys on the keyboard...
Also, on a Mac, the Delete key works the same way the Backspace key does on a Windows PC (i.e. it deletes the character to the left of the cursor). If you want to do a delete on a Mac the same way the Del key does on a Windows PC (i.e. delete the character to the right of the cursor), you have to hold down the Fn key and press the Delete key.
Finally, if you ever wanted to make a screenshot of the screen on a Mac, here's how:
WikiHow:
"How to Take a Screenshot in Mac OS X"