Android (rooted): If you root your phone and install a new ROM, the first thing you may notice is that all of the Google apps you're used to may not be there. Gapps Manager is a utility that will make sure you get the right ones for your device and version of Android.
Gapps Manager isn't the only utility that makes downloading and installing the right Google Apps package (which includes things such as Google Search, Gmail, Google Play, Play Music and so on) a simple process, but it's certainly one of the easiest to use. Once installed, just select the version of the OS your ROM is running (down to the point-version), and the app will handle the rest. It even supports the latest Google Apps compatible with KitKat's new ART compiler. All you have to do is pick the right version and you'll be set up in no time.
The app is free, and it definitely beats searching the web for a reputable download and sideloading the way you used to have to do it. Hit the link below to grab it from Google Play, or to head to the XDA forums and read more about how it works.