The line is west to east, with the first point being west, the second being east.
In the northern hemisphere. Hold the watch horizontally, and point the hour hand towards the sun. The direction that lies midway between the hour hand and 12 o’clock on your watch is south. From there, you can easily determine the other directions. In the southern hemisphere. Hold the watch horizontally, and point the twelve o’clock mark at the sun. The direction that lies halfway between 12 o’clock and the hour hand will be north.
Get yourself a Qibla compass. Find out the direction to Mecca from you location. Hold out your compass flat, wait for the dial to settle. Turn towards the direction to Makkah for your location. Done.
There are over a dozen different iPhone or iPad free apps (look like Athan Pro or Qibla) that will use the built-in GPS and compass to point in exactly the correct direction no matter where in the world you are. The internet has sites that will calculate the direction that is shortest distance to al Qiblah.