I actually wrote an article about this very subject for Wedshed. First and foremost, the weather has to be right for this on the wedding day. It cannot be done when it is overcast, or raining. Second of all it is all about timing, the best light is during the golden hour, which is the 30mins before and after sunset. You can quite easily search for the sunset times and check when sunset will be on your wedding day. Thirdly it comes down to timing, there needs to be enough time during this ‘golden hour’ or around that time of the day to be able to capture the light as it dramatically changes. Quite often it might be a few minutes after you leave that the light gets truly amazing, so it is worth having a buffer of time to be able to accommodate and utilize this to the fullest. Finally it comes down to location, a spot where you can see the setting sun or catch the last of that light as it warms up the landscape and falls away behind the horizon. It can be quite easy to be hidden in the shade or in a spot where that light never really falls (think beach in the East with hills/cliffs blocking the afternoon light).
I know a lot about light and am always happy to plan a location and time to make the most of it. I love shooting in amazing light, and my photos certainly reflect this.