A couple of exceptions: If your phone has a physical Menu button, some options in applications will remain hidden behind that button, as they have in the past. You can press the Menu button in various applications to see what additional options are available to you.
If your phone has a physical Home button but no Recent Apps button, meanwhile, you can access the app-switching function by pressing the Home button and holding it down for a few seconds.
Android 4.0 notifications
Notifications have always been a strength of Android, and with Android 4.0, they become more powerful than ever. Notifications appear on the left side of the status bar at the top of your phone's screen. The icons you see here indicate everything from new email and text messages to missed calls and calendar appointments.
Swiping down on the notification bar gives you detailed information about your pending notifications. Click to view larger image.
To view your notifications in detail, touch your finger to the Notification bar and swipe downward. A panel will pull down over your screen showing you all of your pending notifications; you can tap on any notification to view more information about it or swipe your finger left or right on it to dismiss it from the list. You can also tap the "X" at the top-right of the notification area to dismiss and remove all of your pending notifications.
The type of notifications you get depends on what apps and accounts you have configured on your phone. With any app that's capable of sending notifications, you can customize what events trigger notifications or even disable notifications altogether; just look in the settings of each individual app to find those options.
You can customize or disable notifications within the settings of individual apps. Click to view larger image.
In Gmail, for example, you can tap on the vertical-dots icon at the bottom of the screen (or press the Menu button, if you're on an older phone) to access the app's settings.
Within the Settings menu, tap on the line representing your Gmail account -- if you have more than one Gmail account configured, you can control notifications separately for each one -- and then check or uncheck "Email notifications" to enable or disable notifications for that account. You can also configure whether a sound and/or vibration will accompany each new mail notification.
Similar controls exist in other notification-capable apps, including the Messaging app (for text messages), Google Voice, Google+, Facebook, and most Twitter clients.
The Android 4.0 notifications area can display active controls, such as playback commands for audio applications. Click to view larger image.
In addition to basic activity-based alerts, the notifications area can display active controls for certain types of apps, such as the Android Play Music app; when you're playing a song in that app, pulling down the notification panel will reveal a set of interactive playback controls that allow you to pause, play or stop the music, or navigate through the album's tracks.
Apps in Android 4.0
If the home screen is the heart of Android, the apps are the blood that pump through its veins. Much of the Android experience revolves around applications, whether they're basic system apps like the Phone and Browser apps or third-party apps like Dropbox, Flipboard and Google Reader.