Finding good maps is a constant struggle:
Pick up some of the free maps at the airport.
Tourism centres often provide free maps.
Country travel websites may have good maps.
Google Maps is useful, and you can download maps, but sometimes fails, e.g.:
GPS failure
Cannot download maps for some countries (Thailand and Japan).
Bangkok BTS train station names are in Thai language!
Alternatives to Google Maps include:
OpenStreetMap is a free worldwide map, created by users.
Indoor maps include:
airports,
shopping centres,
malls,
department stores.
Also available is information on local businesses, 3D maps and Street View.
Maps can be downloaded for use without internet connection.