Anywhere you see just about ANY little icon, button, arrow or tiny triangle, try clicking and/or ALT+Clicking on them to see what secrets they hold.
Also, have a look at EVERY Menu item, and give them a try. Just don't "Save" and close your image and you will always be able to go back to your original unedited state by clicking the image at the very top of your History Palette.
Don't forget to give the Help files a thorough scan while you're exploring, too.