Use Android Device Manager or a third-party lost phone app, such as Plan B, to find a lost Android phone. Calling the phone and listening for the ringer is another option.
Device Manager is an Android app that allows users to view their lost phones on a map. Users can access this map using any device by signing into the Google account associated with the phone. The app also allows the user to remotely reset the lock PIN on the device screen or erase all data on the phone, which can help to protect the user's privacy if the phone falls into the wrong hands.
Plan B is another app that helps to locate lost Android phones. Use another device to log into the Google account associated with the lost phone, then install the app. Plan B starts automatically and sends the phone's location to the Gmail address associated with the lost phone. The app uses both GPS and cell towers to locate the phone, so it still works even if GPS is turned off.
A third option is to simply call the Android phone and listen carefully. If the phone is nearby and turned on, it should be possible to hear it ringing or vibrating.