If you've used Android before, you might be wondering what happened to the Menu button. As of Android 4.0, the Menu button is a thing of the past: All options and commands now appear on-screen instead of being hidden away like they were with previous-generation devices.
If an application has more options than can fit on the screen, you'll see an icon that looks like three vertical dots; tapping that icon will bring up a list of additional functions relevant to your current activity.
(Curiously enough, the location of the vertical-dots icon is not always consistent, which was one of my criticisms of ICS in my initial review of the software.)
If your phone has hardware buttons: It's worth noting that while Google's Android 4.0 design guidelines call for virtual on-screen buttons, some phones still use hardware buttons instead -- either because they're older devices that have been upgraded or newer phones whose manufacturers have opted to stick with the older-style setup. If you're using an Android device that has physical buttons, those buttons should more or less correspond with the same functions described above.
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.
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.
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.
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.