The Sleep/Wake button is on the top of the iPad on the side. If the iPad is off and you press it, it turns on. If it's on and you press it, it turns off. If you hold the Sleep/Wake button down, it shuts down your iPad. It's probably not a bad thing to "reboot" every few days.
In the top right hand corner on the side of the iPad is the "Slide Switch". I think that switch mutes your iPad, which can be helpful if you're working with it in a quiet setting.
Just under the switch is the Volume Up/Down switch, which controls the volume. When I plug my iPod into a speaker jack, it will often ignore this setting and go to whichever setting it was on the last time it was plugged into a speaker.
On the top left is a "SIM Tray". I assume that's where you stick in a SIM card if you need removable memory. Unfortunately, I haven't played with that to see exactly how it works.
On the face of the iPad in the center at the bottom is the "home" button. "Home" does something slightly different depending on what you're doing.
If you are on the home screen, it will take you to the search screen.
If you are on the search screen, it will take you back to the home screen.
If you are looking at your apps on the iPad, and your press the Home button, it will take you back to your "Home" screen.
If you are running an App and you press the Home button, you'll go back to the spot where you initiated the Application (possibly the Home screen).
If your iPad is off and you press the home button twice, the iPad will start playing music out of your music library.
If your iPad is on and you press the home button twice, it will display the most recent applications you've accessed.
If your iPad is on and you have something interesting on the screen, you can press the Home button and the On/Off button at the same time and it will take a picture of the screen and save it to Photos.
Hard Reboot. If your iPad is locked up or won't come on, hold the On/Off button and the Home button down together for 30 seconds. This should force your iPad to reboot.
What's your favorite button combination?