1 - Go to Google map
2 - Double click the location whose latitude and longitude you need to find. The latitude (on the left) and the longitude are in the URL box as shown below.
Fig.1 - Latitude and Longitude of New York City in the USA
or
3 - Right click the location whose latitude and longitude you need to find. A small box shows the latitude and longitude at the top as shown below.
Fig.2 - Latitude and Longitude of Mexico City in Mexico
A - Using a Smartphone
1 - Go to Google map
2 - Type the address (or name such as London UK) of the location in the search box or select a location on the map and hold down to get the red pin on the map at the selected location.
The latitude and longitude are displayed in the search box.
Fig.3 - Latitude and Longitude of London City in the UK