Use another cell phone and send a text message with the text "findme(case sensitive)", your lost phone will change its profile and start ringing your default ring tone.
If you have dropped your phone and you want the accurate location to find it:
Send a Text Message from another cell phone with the text "locateme(case sensitive)", if your phone is still turned On then it will reply you back with a Link of Google Earth with its location. Open this link in any browser to see your phone's location via Google Earth. There is only one catch, if you have turned off your location services then this app will not be able to provide you its location as it's a dependency from Google.