By default you are locked in portrait mode, o switch to landscape, pull down the notification bar and then tap on the orientation icon next to the date. You can also unlock the orientation via Settings > Accessibility > Auto-rotate.
Access Recent Apps
Press the button to the right of the Home button to get a pop up list of your most recently opened apps. You can tap on them to re-launch, swipe them off to the right to close them, and you can press and hold your finger on them to access more info or bring up the full app menu. The full app menu lets you choose to uninstall or clear data, among other things.
Disable Pre-Installed Apps
Go to Settings > Apps and swipe to the All tab to find the app you want to disable. Tap on the app, select ‘disable,’ then click OK. The app will hibernate and the icon will be removed from your home screen and the app drawer.
If you find that you want to re-activate it for any reason, just go back to Settings > Apps, swipe to All, then scroll to the bottom to find disabled apps.
Take a Screen Shot
Hold the power and volume down buttons for two seconds to take a screen shot.
Kill a Running App
To shut down an app manually, open Settings, press Apps under Device, select the app you want to close, press the "Force stop" button, and choose OK.
Long-press an app and slide it on another app. Now you have a folder with two apps inside. You can long-press and slide multiple apps into your newly created folder.
To name your folder, tap once. You will see “Unnamed Folder” just below all your apps. Tap on it once and enter the desired name using the onscreen keyboard. Press “Done” and tap outside the folder. To remove all apps from your folder, simply long-press an app and move it outside the folder.
These seemed the most useful tips, but if you want me to add anything please ask in the comments.