Android 4.4 includes a default launcher option in the Settings menu, but earlier versions store this data in your launcher's Application Info menu. The first time you launch an app after installing a new launcher, Android prompts you to choose a default method for completing the action. Use this prompt or the Settings menu to choose a default launcher depending on your version of Android.
Try Several Launchers
In all Android versions, your default launcher stores its status as default in the Application Info menu and saves this information when you choose a default launcher from the pop-up window after launching an app. Tap "Settings," "Applications" and "Manage Applications," then choose your launcher to open the Application Info menu. Tap "Clear Defaults" under Launch by Default to remove this launcher's setting as the default. After installing a second, new launcher, the next time you open an app Android prompts you to choose a new default launcher. In Android 4.4, use this method or the simpler Home menu option to set a launcher as default: tap "Settings," choose "Home" and select a launcher; this option offers a quicker way to switch between launchers so that you can explore several launchers' features.
Switch Between Many Themes
ADW, Go and Nova offer free and premium launchers that manage your background, home screens, app drawer and icon themes (links in Resources). Each launcher stores these preferences in its respective settings menu so that changing your default launcher also changes Android's look and feel. Customize your device's theme by opening your default launcher's settings menu and exploring its options. Different launchers offer varying color and icon theme settings as well as launch animations and screen transitions -- many of these effects work best on new devices and tend to look choppy on older hardware.