This one needs no explanation - there is a high chance you already have Google Maps on your phone right now. Use it to get around and navigate your way around whatever city or country you're at.

No data? No problem! Here's a little tip - the Google Maps iOS app has an offline map feature (Android should have it as well). While you have internet, click on the search bar at the top of the screen and your recent search history and nearby places should display. Just scroll down the screen and at the bottom you should see the option to 'Save a new offline map'. Hit that button, pan/zoom to the area you wish to save, and then hit 'Save'. The cached map is now available even when you don't have internet - but make sure you have GPS enabled (GPS is always free and doesn't require a SIM/phone connection).

App download link: http://www.google.com/mobile/maps/