When you install a 3rd party launcher, whenever you hit the "Home" button a pop-up will appear asking you to select which Launcher to use. It will also ask you to select whether you want to use that app just that one time or all the time (set it as default). If you want to go back after you set something else to default (for instance, say you install GoLauncher, press Home and select "Always"), all you have to do is go to your Settings, Application Manager, find the 3rd party app and select "Clear Defaults". This option restores the pop-up and you can select another launcher when pressing the home button. The same method applies to everything else that can be handled by several apps in your phone (web links, photos, etc.)